From 6e7161f52c3535c6fbd82c12fa152e070d21be20 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Tue, 2 Feb 2021 14:28:23 +0100 Subject: [PATCH 01/13] add header, main, footer sectoins --- index.html | 91 ++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 71 insertions(+), 20 deletions(-) diff --git a/index.html b/index.html index 67dfc7f5..f5424aa6 100644 --- a/index.html +++ b/index.html @@ -1,22 +1,73 @@ - - - - My Blog - - - - - - - - - + + + + + My Blog + + + + + + + + +
+

Lorem Ipsum

+ +
+ +
+

What is Lorem Ipsum? + Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's + standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a + type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, + remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing + Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions + of + Lorem Ipsum.

+ +

Why do we use it? + It is a long established fact that a reader will be distracted by the + readable content of a page when looking at its layout. + The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, + as opposed to using 'Content here, content here', making it look like readable English. + Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, + and a search for 'lorem ipsum' will uncover many web sites still in their infancy. + Various versions have evolved over the years, sometimes by accident, + sometimes on purpose (injected humour and the like).>

+ + +

Where does it come from? + Contrary to popular belief, Lorem Ipsum is not simply random text. + It has roots in a piece of classical Latin literature from 45 BC, + making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney + College in Virginia, looked up one of the more obscure Latin words, consectetur, + from a Lorem Ipsum passage, and going through the cites of the word in classical literature, + discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and + 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, + written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. + The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

+ +

The standard chunk of Lorem Ipsum used since the 1500s is reproduced + below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus + Bonorum et Malorum" by Cicero are also reproduced in their exact original form, + accompanied by English versions from the 1914 translation by H. Rackham.

+ +
+ + + + + \ No newline at end of file From 3fbdbf3b81823f0081a8d87b671885d32a8dbba8 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Tue, 2 Feb 2021 14:39:00 +0100 Subject: [PATCH 02/13] add nav section --- index.html | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/index.html b/index.html index f5424aa6..07e0698f 100644 --- a/index.html +++ b/index.html @@ -14,13 +14,16 @@
-

Lorem Ipsum

+

Newton's laws of motion

+ Isaac Newton From e66e6bb366d4db4643324ceb62318e5b5137f25f Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Tue, 2 Feb 2021 14:48:27 +0100 Subject: [PATCH 03/13] add text information --- index.html | 153 ++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 116 insertions(+), 37 deletions(-) diff --git a/index.html b/index.html index 07e0698f..fcfcac0e 100644 --- a/index.html +++ b/index.html @@ -15,7 +15,8 @@

Newton's laws of motion

- Isaac Newton + Isaac Newton
-

What is Lorem Ipsum? - Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's - standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a - type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, - remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing - Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions - of - Lorem Ipsum.

- -

Why do we use it? - It is a long established fact that a reader will be distracted by the - readable content of a page when looking at its layout. - The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, - as opposed to using 'Content here, content here', making it look like readable English. - Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, - and a search for 'lorem ipsum' will uncover many web sites still in their infancy. - Various versions have evolved over the years, sometimes by accident, - sometimes on purpose (injected humour and the like).>

- - -

Where does it come from? - Contrary to popular belief, Lorem Ipsum is not simply random text. - It has roots in a piece of classical Latin literature from 45 BC, - making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney - College in Virginia, looked up one of the more obscure Latin words, consectetur, - from a Lorem Ipsum passage, and going through the cites of the word in classical literature, - discovered the undoubtable source. Lorem Ipsum comes from sections 1.10.32 and - 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) by Cicero, - written in 45 BC. This book is a treatise on the theory of ethics, very popular during the Renaissance. - The first line of Lorem Ipsum, "Lorem ipsum dolor sit amet..", comes from a line in section 1.10.32.

- -

The standard chunk of Lorem Ipsum used since the 1500s is reproduced - below for those interested. Sections 1.10.32 and 1.10.33 from "de Finibus - Bonorum et Malorum" by Cicero are also reproduced in their exact original form, - accompanied by English versions from the 1914 translation by H. Rackham.

+ +

In classical mechanics, Newton's laws of motion are three laws that describe the relationship + between the motion of an object and the forces acting on it. The first law states that an object + either remains at rest or continues to move at a constant velocity, + unless it is acted upon by an external force. The second law states that the rate of change + f momentum of an object is directly proportional to the force applied, or, for an object with + constant mass, that the net force on an object is equal to the mass of that object multiplied + by the acceleration. The third law states that when one object exerts a force on a second object, + that second object exerts a force that is equal in magnitude and opposite in direction on the first object. +

+

+ The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia + Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. + Newton used them to explain and investigate the motion of many physical objects and systems, + which laid the foundation for Newtonian mechanics. +

+ +

The First Law

+

The first law states that an object at rest will stay at rest, and an object in motion will + stay in motion unless acted on by a net external force. Mathematically, + this is equivalent to saying that if the net force on an object is zero, + then the velocity of the object is constant. + + {\displaystyle \sum \mathbf {F} =0\;\Leftrightarrow \;{\frac {\mathrm {d} \mathbf {v} }{\mathrm {d} t}}=0.}\sum + \mathbf {F} =0\;\Leftrightarrow \;{\frac {\mathrm {d} \mathbf {v} }{\mathrm {d} t}}=0. + Newton's first law is often referred to as the law of inertia. + + Newton's first (and second) laws are valid only in an inertial reference frame.[4]

+ +

The Second Law

+

The second law states that the rate of change of momentum of a body over time is directly + proportional to the force applied, and occurs in the same direction as the applied force. + + {\displaystyle \mathbf {F} ={\frac {\mathrm {d} \mathbf {p} }{\mathrm {d} t}}}{\displaystyle \mathbf {F} ={\frac + {\mathrm {d} \mathbf {p} }{\mathrm {d} t}}} + Constant Mass + For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an object's + acceleration. + + {\displaystyle \mathbf {F} ={\frac {\mathrm {d} (m\mathbf {v} )}{\mathrm {d} t}}=m\,{\frac {\,\mathrm {d} \mathbf + {v} \,}{\mathrm {d} t}}=m\mathbf {a} ,}{\displaystyle \mathbf {F} ={\frac {\mathrm {d} (m\mathbf {v} )}{\mathrm + {d} + t}}=m\,{\frac {\,\mathrm {d} \mathbf {v} \,}{\mathrm {d} t}}=m\mathbf {a} ,} + where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net force + applied to a body produces a proportional acceleration. + + Variable-mass systems + Main article: Variable-mass system + Variable-mass systems, like a rocket burning fuel and ejecting spent gases, + are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] The + equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is obtained by + applying the second law to the entire, constant-mass system consisting of the body and its ejected or accreted + mass; + the result is[5] + + {\displaystyle \mathbf {F} +\mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}=m{\mathrm {d} \mathbf {v} \over + \mathrm {d} t}}\mathbf {F} +\mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}=m{\mathrm {d} \mathbf {v} \over + \mathrm {d} t} + where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation one can + derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. + + Under some conventions, the quantity {\displaystyle \mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} + t}}}{\displaystyle \mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}} on the left-hand side, which represents the + advection of momentum, is defined as a force (the force exerted on the body by the changing mass, such as rocket + exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the equation + becomes F = ma. +

+ +

The Third Law

+

The third law states that all forces between two objects exist in equal magnitude and opposite direction: if one + object A exerts a force FA on a second object B, then B simultaneously exerts a force FB on A, and the two forces + are equal in magnitude and opposite in direction: FA = −FB.[8] The third law means that all forces are + interactions between different bodies,[9][10] or different regions within one body, and thus that there is no such + thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude and + direction of the forces are determined entirely by one of the two bodies, say Body A; the force exerted by Body A + on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This law is + sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In other + situations the magnitude and directions of the forces are determined jointly by both bodies and it isn't necessary + to identify one force as the "action" and the other as the "reaction". The action and the reaction are + simultaneous, and it does not matter which is called the action and which is called reaction; both forces are part + of a single interaction, and neither force exists without the other.[8] + + The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force on + an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires + pushing backward on the road). + + From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, and the + floor pushes against the person. Similarly, the tires of a car push against the road while the road pushes back on + the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with the + water, pushing the water backward, while the water simultaneously pushes the person forward—both the person and + the water push against each other. The reaction forces account for the motion in these examples. These forces + depend on friction; a person or car on ice, for example, may be unable to exert the action force to produce the + needed reaction force.[11] + + Newton used the third law to derive the law of conservation of momentum;[12] from a deeper perspective, however, + conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), + and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles + carry momentum, and in quantum mechanics.

+ +

History

+

The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the universe: that + heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted to be at + rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state + when it was at rest, and for the body to move in a straight line at a constant speed an external agent was needed + continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force is + necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its velocity. + In other words, Galileo stated that, in the absence of a force, a moving object will continue moving. (The + tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight was + refined by Newton, who made it into his first law, also known as the "law of inertia"—no force means no + acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the law of + inertia which Galileo had already described, Newton appropriately gave credit to Galileo.

+ +
- +
From ad81b8bc22bb6e396aed3bda43651f1b8e40c494 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Tue, 2 Feb 2021 16:02:49 +0100 Subject: [PATCH 04/13] add formuls and links --- css/style.css | 28 ++++ index.html | 367 ++++++++++++++++++++++++++++++-------------------- 2 files changed, 250 insertions(+), 145 deletions(-) diff --git a/css/style.css b/css/style.css index 75e9841e..a8138eb2 100644 --- a/css/style.css +++ b/css/style.css @@ -6,3 +6,31 @@ * for example: General styles, Navigation styles, Hero styles, Footer etc. * */ + + +.header, +.footer { + background-color: grey; + color: white; + padding: 15px; +} + +p { + font-size: 125%; + margin-bottom: 3em; +} + +.math { + display: inline-block; +} + +img { + float: left; + margin: 0 auto; + +} + +main { + + margin: 2em 2em 3em 2em; +} \ No newline at end of file diff --git a/index.html b/index.html index fcfcac0e..f025fd9f 100644 --- a/index.html +++ b/index.html @@ -1,155 +1,232 @@ + + + - - My Blog + + + Newton's laws of motion - - - - - -
-

Newton's laws of motion

- Isaac Newton - -
- -
- -

In classical mechanics, Newton's laws of motion are three laws that describe the relationship - between the motion of an object and the forces acting on it. The first law states that an object - either remains at rest or continues to move at a constant velocity, - unless it is acted upon by an external force. The second law states that the rate of change - f momentum of an object is directly proportional to the force applied, or, for an object with - constant mass, that the net force on an object is equal to the mass of that object multiplied - by the acceleration. The third law states that when one object exerts a force on a second object, - that second object exerts a force that is equal in magnitude and opposite in direction on the first object. -

-

- The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia - Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. - Newton used them to explain and investigate the motion of many physical objects and systems, - which laid the foundation for Newtonian mechanics. -

- -

The First Law

-

The first law states that an object at rest will stay at rest, and an object in motion will - stay in motion unless acted on by a net external force. Mathematically, - this is equivalent to saying that if the net force on an object is zero, - then the velocity of the object is constant. - - {\displaystyle \sum \mathbf {F} =0\;\Leftrightarrow \;{\frac {\mathrm {d} \mathbf {v} }{\mathrm {d} t}}=0.}\sum - \mathbf {F} =0\;\Leftrightarrow \;{\frac {\mathrm {d} \mathbf {v} }{\mathrm {d} t}}=0. - Newton's first law is often referred to as the law of inertia. - - Newton's first (and second) laws are valid only in an inertial reference frame.[4]

- -

The Second Law

-

The second law states that the rate of change of momentum of a body over time is directly - proportional to the force applied, and occurs in the same direction as the applied force. - - {\displaystyle \mathbf {F} ={\frac {\mathrm {d} \mathbf {p} }{\mathrm {d} t}}}{\displaystyle \mathbf {F} ={\frac - {\mathrm {d} \mathbf {p} }{\mathrm {d} t}}} - Constant Mass - For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an object's - acceleration. - - {\displaystyle \mathbf {F} ={\frac {\mathrm {d} (m\mathbf {v} )}{\mathrm {d} t}}=m\,{\frac {\,\mathrm {d} \mathbf - {v} \,}{\mathrm {d} t}}=m\mathbf {a} ,}{\displaystyle \mathbf {F} ={\frac {\mathrm {d} (m\mathbf {v} )}{\mathrm - {d} - t}}=m\,{\frac {\,\mathrm {d} \mathbf {v} \,}{\mathrm {d} t}}=m\mathbf {a} ,} - where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net force - applied to a body produces a proportional acceleration. - - Variable-mass systems - Main article: Variable-mass system - Variable-mass systems, like a rocket burning fuel and ejecting spent gases, - are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] The - equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is obtained by - applying the second law to the entire, constant-mass system consisting of the body and its ejected or accreted - mass; - the result is[5] - - {\displaystyle \mathbf {F} +\mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}=m{\mathrm {d} \mathbf {v} \over - \mathrm {d} t}}\mathbf {F} +\mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}=m{\mathrm {d} \mathbf {v} \over - \mathrm {d} t} - where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation one can - derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. - - Under some conventions, the quantity {\displaystyle \mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} - t}}}{\displaystyle \mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}} on the left-hand side, which represents the - advection of momentum, is defined as a force (the force exerted on the body by the changing mass, such as rocket - exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the equation - becomes F = ma. -

- -

The Third Law

-

The third law states that all forces between two objects exist in equal magnitude and opposite direction: if one - object A exerts a force FA on a second object B, then B simultaneously exerts a force FB on A, and the two forces - are equal in magnitude and opposite in direction: FA = −FB.[8] The third law means that all forces are - interactions between different bodies,[9][10] or different regions within one body, and thus that there is no such - thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude and - direction of the forces are determined entirely by one of the two bodies, say Body A; the force exerted by Body A - on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This law is - sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In other - situations the magnitude and directions of the forces are determined jointly by both bodies and it isn't necessary - to identify one force as the "action" and the other as the "reaction". The action and the reaction are - simultaneous, and it does not matter which is called the action and which is called reaction; both forces are part - of a single interaction, and neither force exists without the other.[8] - - The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force on - an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires - pushing backward on the road). - - From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, and the - floor pushes against the person. Similarly, the tires of a car push against the road while the road pushes back on - the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with the - water, pushing the water backward, while the water simultaneously pushes the person forward—both the person and - the water push against each other. The reaction forces account for the motion in these examples. These forces - depend on friction; a person or car on ice, for example, may be unable to exert the action force to produce the - needed reaction force.[11] - - Newton used the third law to derive the law of conservation of momentum;[12] from a deeper perspective, however, - conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean invariance), - and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles - carry momentum, and in quantum mechanics.

- -

History

-

The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the universe: that - heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted to be at - rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state - when it was at rest, and for the body to move in a straight line at a constant speed an external agent was needed - continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force is - necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its velocity. - In other words, Galileo stated that, in the absence of a force, a moving object will continue moving. (The - tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight was - refined by Newton, who made it into his first law, also known as the "law of inertia"—no force means no - acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the law of - inertia which Galileo had already described, Newton appropriately gave credit to Galileo.

- - - -
- -
- -
- + + + +
+ +

Newton's laws of motion

+ + +
+ +
+ + Isaac Newton +

In classical mechanics, Newton's laws of motion are three laws that describe the relationship + between the motion of an object and the forces acting on it. The first law states that an object + either remains at rest or continues to move at a constant velocity, + unless it is acted upon by an external force. The second law states that the rate of change + f momentum of an object is directly proportional to the force applied, or, for an object with + constant mass, that the net force on an object is equal to the mass of that object multiplied + by the acceleration. The third law states that when one object exerts a force on a second object, + that second object exerts a force that is equal in magnitude and opposite in direction on the first object. +

+

+ The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia + Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. + Newton used them to explain and investigate the motion of many physical objects and systems, + which laid the foundation for Newtonian mechanics. +

+
+ +

The First Law

+

The first law states that an object at rest will stay at rest, and an object in motion will + stay in motion unless acted on by a net external force. Mathematically, + this is equivalent to saying that if the net force on an object is zero, + then the velocity of the object is constant.

+ +
+ + +

Newton's first law is often referred to as the law of inertia. + Newton's first (and second) laws are valid only in an inertial reference frame.[4]

+ +
+

The Second Law

+

The second law states that the rate of change of momentum of a body over time is directly + proportional to the force applied, and occurs in the same direction as the applied force. + +

+
+ + +

Constant Mass

+

For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an object's + acceleration.

+ + +
+
+ +

where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net + force applied to a body produces a proportional acceleration.

+ +

Variable-mass systems

+ +

Variable-mass systems, like a rocket burning fuel and ejecting spent gases, + are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] The + equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is obtained + by + applying the second law to the entire, constant-mass system consisting of the body and its ejected or accreted + mass; + the result is[5]

+ +
+
+ + +

where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation one + can derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. + Under some conventions, the quantity

+
+
on +

the + left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on the + body + by the changing mass, such as rocket + exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the equation + becomes F = ma. +

+ +
+

The Third Law

+

The third law states that all forces between two objects exist in equal magnitude and opposite direction: if + one + object A exerts a force FA on a second object B, then B simultaneously exerts a force FB on A, and the two + forces + are equal in magnitude and opposite in direction: FA = −FB.[8] The third law means that all forces are + interactions between different bodies,[9][10] or different regions within one body, and thus that there is no + such + thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude and + direction of the forces are determined entirely by one of the two bodies, say Body A; the force exerted by + Body + A + on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This law + is + sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In other + situations the magnitude and directions of the forces are determined jointly by both bodies and it isn't + necessary + to identify one force as the "action" and the other as the "reaction". The action and the reaction are + simultaneous, and it does not matter which is called the action and which is called reaction; both forces are + part + of a single interaction, and neither force exists without the other.[8] + + The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force + on + an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires + pushing backward on the road). + + From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, and + the + floor pushes against the person. Similarly, the tires of a car push against the road while the road pushes + back + on + the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with the + water, pushing the water backward, while the water simultaneously pushes the person forward—both the person + and + the water push against each other. The reaction forces account for the motion in these examples. These forces + depend on friction; a person or car on ice, for example, may be unable to exert the action force to produce + the + needed reaction force.[11] + + Newton used the third law to derive the law of conservation of momentum;[12] from a deeper perspective, + however, + conservation of momentum is the more fundamental idea (derived via Noether's theorem from Galilean + invariance), + and holds in cases where Newton's third law appears to fail, for instance when force fields as well as + particles + carry momentum, and in quantum mechanics.

+
+

History

+

The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the universe: + that + heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted to be + at + rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state + when it was at rest, and for the body to move in a straight line at a constant speed an external agent was + needed + continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force is + necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its + velocity. + In other words, Galileo stated that, in the absence of a force, a moving object will continue moving. (The + tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight was + refined by Newton, who made it into his first law, also known as the "law of inertia"—no force means no + acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the law + of + inertia which Galileo had already described, Newton appropriately gave credit to Galileo.

+ +

Links

+

+

    +
  1. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering and + science (Series: Schaum's Outline Series). McGraw-Hill Companies. p. 58. ISBN 978-0-07-008498-8.
    2. +
  2. the Principia on line at Andrew Motte Translation
    3. +
  3. Andrew Motte translation of Newton's Principia (1687) Axioms or Laws of Motion
    4. +
  4. Thornton, Marion (2004). Classical dynamics of particles and systems (5th ed.). Brooks/Cole. p. 53. + ISBN 978-0-534-40896-1.
    5. + +
  5. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for variable + mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. Bibcode:1992CeMDA..53..227P. + doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's second + law is valid for constant mass only. When the mass varies due to accretion or ablation, [an alternate + equation explicitly accounting for the changing mass] should be used."
    6. +
  6. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we cannot + derive a general expression for Newton's second law for variable mass systems by treating the mass in F = + dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we apply + it to an entire system of constant mass, having parts among which there is an interchange of mass. + [Emphasis as in the original]
    7. +
  7. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. ISBN + 978-0-07-035048-9 – via archive.org. Recall that F = dP/dt was established for a system composed of a + certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the time + interval[. ...] Consequently, the mass of the system can not change during the time of interest.
    8. +
  8. Resnick; Halliday; Krane (1992). Physics, Volume 1 (4th ed.). p. 83.
    9. +
  9. C Hellingman (1992). "Newton's third law revisited". Phys. Educ. 27 (2): 112–115.
    10. +
  10. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is only + one aspect of a mutual interaction between two bodies.
    11. +
  11. Hewitt (2006), p. 75
    12. +
  12. Newton, Principia, Corollary III to the laws of motion
    13. + +
+

+ + + +
+ +
+ +
+ \ No newline at end of file From b71da20d60a59db4452926a94c1d5ca7d30b216c Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Tue, 2 Feb 2021 23:19:49 +0100 Subject: [PATCH 05/13] crate horizontal menu --- css/style.css | 87 ++++++++++++++++++++++++++++-- index.html | 147 +++++++++++++++++++++++++++++++------------------- 2 files changed, 175 insertions(+), 59 deletions(-) diff --git a/css/style.css b/css/style.css index a8138eb2..eeef48ea 100644 --- a/css/style.css +++ b/css/style.css @@ -15,9 +15,88 @@ padding: 15px; } +h1 { + font-size: 300%; + text-align: center; +} +nav { + display: block; + width: 660px; + margin: 0 auto 30px; +} + +body { + margin: 0; +} + +h2 { + font-family: monospace; + color: #606060; + margin-top: 2em; + margin-bottom: 5em; +} + +hr { + margin-top: 5em; +} + +ul { + list-style: none; + margin: 0 auto; +} + +a { + text-decoration: none; + font-family: 'Lora', serif; + transition: .5s linear; +} + +nav { + display: block; + width: 660px; + margin: 0 auto 30px; +} + +.one ul { + padding: 1em 0; + background: #ECDAD6; +} + +.one a { + padding: 1em; + background: rgba(177, 152, 145, .3); + border-right: 1px solid #b19891; + color: #695753; +} + +.one a:hover { + background: #b19891; +} + +.one li { + display: inline; +} + +.one ul { + list-style: none; + margin: 0; + padding-left: 0; + display: block; +} + +li { + display: inline; +} + +a { + font-family: 'Lora', serif; + transition: .5s linear; + text-decoration: none; +} + p { - font-size: 125%; - margin-bottom: 3em; + font-size: 150%; + } .math { @@ -25,8 +104,8 @@ p { } img { - float: left; - margin: 0 auto; + float: right; + margin: 20px; } diff --git a/index.html b/index.html index f025fd9f..3ca75cfc 100644 --- a/index.html +++ b/index.html @@ -17,19 +17,19 @@ -
+

Newton's laws of motion

-
@@ -37,7 +37,7 @@

Newton's laws of motion

Isaac Newton + alt="Isaac Newton" height="400px">

In classical mechanics, Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, @@ -46,8 +46,6 @@

Newton's laws of motion

constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration. The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object. -

-

The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems, @@ -55,21 +53,22 @@

Newton's laws of motion

-

The First Law

+

The First Law

The first law states that an object at rest will stay at rest, and an object in motion will stay in motion unless acted on by a net external force. Mathematically, this is equivalent to saying that if the net force on an object is zero, then the velocity of the object is constant.

+ src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cf29dd89fdaf777f52adebc3735e4b63d3ef8810"> +

Newton's first law is often referred to as the law of inertia. Newton's first (and second) laws are valid only in an inertial reference frame.[4]

-

The Second Law

+

The Second Law

The second law states that the rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force. @@ -79,7 +78,8 @@

The Second Law

Constant Mass

-

For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an object's +

For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an + object's acceleration.

@@ -87,16 +87,20 @@

Constant Mass

src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0ca4b7a15aad6089d7d5efc8c2d7366d72717b83"> -

where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net +

where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the + net force applied to a body produces a proportional acceleration.

Variable-mass systems

Variable-mass systems, like a rocket burning fuel and ejecting spent gases, - are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] The - equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is obtained + are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] + The + equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is + obtained by - applying the second law to the entire, constant-mass system consisting of the body and its ejected or accreted + applying the second law to the entire, constant-mass system consisting of the body and its ejected or + accreted mass; the result is[5]

@@ -105,58 +109,74 @@

Variable-mass systems

-

where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation one +

where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation + one can derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. Under some conventions, the quantity

on

the - left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on the + left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on + the body by the changing mass, such as rocket - exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the equation + exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the + equation becomes F = ma.

-

The Third Law

-

The third law states that all forces between two objects exist in equal magnitude and opposite direction: if +

The Third Law

+

The third law states that all forces between two objects exist in equal magnitude and opposite direction: + if one object A exerts a force FA on a second object B, then B simultaneously exerts a force FB on A, and the two forces are equal in magnitude and opposite in direction: FA = −FB.[8] The third law means that all forces are - interactions between different bodies,[9][10] or different regions within one body, and thus that there is no + interactions between different bodies,[9][10] or different regions within one body, and thus that there is + no such - thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude and + thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude + and direction of the forces are determined entirely by one of the two bodies, say Body A; the force exerted by Body A - on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This law + on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This + law is - sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In other + sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In + other situations the magnitude and directions of the forces are determined jointly by both bodies and it isn't necessary to identify one force as the "action" and the other as the "reaction". The action and the reaction are - simultaneous, and it does not matter which is called the action and which is called reaction; both forces are + simultaneous, and it does not matter which is called the action and which is called reaction; both forces + are part of a single interaction, and neither force exists without the other.[8] - The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force + The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional + force on - an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires + an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the + tires pushing backward on the road). - From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, and + From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, + and the floor pushes against the person. Similarly, the tires of a car push against the road while the road pushes back on - the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with the - water, pushing the water backward, while the water simultaneously pushes the person forward—both the person + the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with + the + water, pushing the water backward, while the water simultaneously pushes the person forward—both the + person and - the water push against each other. The reaction forces account for the motion in these examples. These forces - depend on friction; a person or car on ice, for example, may be unable to exert the action force to produce + the water push against each other. The reaction forces account for the motion in these examples. These + forces + depend on friction; a person or car on ice, for example, may be unable to exert the action force to + produce the needed reaction force.[11] @@ -168,51 +188,68 @@

The Third Law

particles carry momentum, and in quantum mechanics.

-

History

-

The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the universe: +

History

+

The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the + universe: that - heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted to be + heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted + to be at - rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state + rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural + state when it was at rest, and for the body to move in a straight line at a constant speed an external agent was needed - continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force is + continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force + is necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its velocity. In other words, Galileo stated that, in the absence of a force, a moving object will continue moving. (The - tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight was + tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight + was refined by Newton, who made it into his first law, also known as the "law of inertia"—no force means no - acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the law + acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the + law of inertia which Galileo had already described, Newton appropriately gave credit to Galileo.

-

Links

+
+

    -
  1. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering and +
  2. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering + and science (Series: Schaum's Outline Series). McGraw-Hill Companies. p. 58. ISBN 978-0-07-008498-8.
  3. the Principia on line at Andrew Motte Translation
  4. Andrew Motte translation of Newton's Principia (1687) Axioms or Laws of Motion
  5. Thornton, Marion (2004). Classical dynamics of particles and systems (5th ed.). Brooks/Cole. p. 53. ISBN 978-0-534-40896-1.
    6. -
  6. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for variable - mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. Bibcode:1992CeMDA..53..227P. - doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's second +
  7. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for + variable + mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. + Bibcode:1992CeMDA..53..227P. + doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's + second law is valid for constant mass only. When the mass varies due to accretion or ablation, [an alternate equation explicitly accounting for the changing mass] should be used."
    8. -
  8. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we cannot - derive a general expression for Newton's second law for variable mass systems by treating the mass in F = - dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we apply +
  9. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we + cannot + derive a general expression for Newton's second law for variable mass systems by treating the mass in + F = + dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we + apply it to an entire system of constant mass, having parts among which there is an interchange of mass. [Emphasis as in the original]
    10. -
  10. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. ISBN +
  11. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. + ISBN 978-0-07-035048-9 – via archive.org. Recall that F = dP/dt was established for a system composed of a - certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the time + certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the + time interval[. ...] Consequently, the mass of the system can not change during the time of interest.
  12. Resnick; Halliday; Krane (1992). Physics, Volume 1 (4th ed.). p. 83.
  13. C Hellingman (1992). "Newton's third law revisited". Phys. Educ. 27 (2): 112–115.
    14. -
  14. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is only +
  15. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is + only one aspect of a mutual interaction between two bodies.
  16. Hewitt (2006), p. 75
  17. Newton, Principia, Corollary III to the laws of motion
    18. From 4d0ed5c824bcb1ee48918e65b98b5178a768b7ea Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Tue, 2 Feb 2021 23:19:49 +0100 Subject: [PATCH 06/13] create horizontal menu --- css/style.css | 87 ++++++++++++++++++++++++++++-- index.html | 147 +++++++++++++++++++++++++++++++------------------- 2 files changed, 175 insertions(+), 59 deletions(-) diff --git a/css/style.css b/css/style.css index a8138eb2..eeef48ea 100644 --- a/css/style.css +++ b/css/style.css @@ -15,9 +15,88 @@ padding: 15px; } +h1 { + font-size: 300%; + text-align: center; +} +nav { + display: block; + width: 660px; + margin: 0 auto 30px; +} + +body { + margin: 0; +} + +h2 { + font-family: monospace; + color: #606060; + margin-top: 2em; + margin-bottom: 5em; +} + +hr { + margin-top: 5em; +} + +ul { + list-style: none; + margin: 0 auto; +} + +a { + text-decoration: none; + font-family: 'Lora', serif; + transition: .5s linear; +} + +nav { + display: block; + width: 660px; + margin: 0 auto 30px; +} + +.one ul { + padding: 1em 0; + background: #ECDAD6; +} + +.one a { + padding: 1em; + background: rgba(177, 152, 145, .3); + border-right: 1px solid #b19891; + color: #695753; +} + +.one a:hover { + background: #b19891; +} + +.one li { + display: inline; +} + +.one ul { + list-style: none; + margin: 0; + padding-left: 0; + display: block; +} + +li { + display: inline; +} + +a { + font-family: 'Lora', serif; + transition: .5s linear; + text-decoration: none; +} + p { - font-size: 125%; - margin-bottom: 3em; + font-size: 150%; + } .math { @@ -25,8 +104,8 @@ p { } img { - float: left; - margin: 0 auto; + float: right; + margin: 20px; } diff --git a/index.html b/index.html index f025fd9f..3ca75cfc 100644 --- a/index.html +++ b/index.html @@ -17,19 +17,19 @@ -
    +

    Newton's laws of motion

    -
    @@ -37,7 +37,7 @@

    Newton's laws of motion

    Isaac Newton + alt="Isaac Newton" height="400px">

    In classical mechanics, Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, @@ -46,8 +46,6 @@

    Newton's laws of motion

    constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration. The third law states that when one object exerts a force on a second object, that second object exerts a force that is equal in magnitude and opposite in direction on the first object. -

    -

    The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. Newton used them to explain and investigate the motion of many physical objects and systems, @@ -55,21 +53,22 @@

    Newton's laws of motion

    -

    The First Law

    +

    The First Law

    The first law states that an object at rest will stay at rest, and an object in motion will stay in motion unless acted on by a net external force. Mathematically, this is equivalent to saying that if the net force on an object is zero, then the velocity of the object is constant.

    + src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cf29dd89fdaf777f52adebc3735e4b63d3ef8810"> +

    Newton's first law is often referred to as the law of inertia. Newton's first (and second) laws are valid only in an inertial reference frame.[4]

    -

    The Second Law

    +

    The Second Law

    The second law states that the rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force. @@ -79,7 +78,8 @@

    The Second Law

    Constant Mass

    -

    For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an object's +

    For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an + object's acceleration.

    @@ -87,16 +87,20 @@

    Constant Mass

    src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0ca4b7a15aad6089d7d5efc8c2d7366d72717b83"> -

    where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net +

    where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the + net force applied to a body produces a proportional acceleration.

    Variable-mass systems

    Variable-mass systems, like a rocket burning fuel and ejecting spent gases, - are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] The - equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is obtained + are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] + The + equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is + obtained by - applying the second law to the entire, constant-mass system consisting of the body and its ejected or accreted + applying the second law to the entire, constant-mass system consisting of the body and its ejected or + accreted mass; the result is[5]

    @@ -105,58 +109,74 @@

    Variable-mass systems

    -

    where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation one +

    where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation + one can derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. Under some conventions, the quantity

    on

    the - left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on the + left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on + the body by the changing mass, such as rocket - exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the equation + exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the + equation becomes F = ma.

    -

    The Third Law

    -

    The third law states that all forces between two objects exist in equal magnitude and opposite direction: if +

    The Third Law

    +

    The third law states that all forces between two objects exist in equal magnitude and opposite direction: + if one object A exerts a force FA on a second object B, then B simultaneously exerts a force FB on A, and the two forces are equal in magnitude and opposite in direction: FA = −FB.[8] The third law means that all forces are - interactions between different bodies,[9][10] or different regions within one body, and thus that there is no + interactions between different bodies,[9][10] or different regions within one body, and thus that there is + no such - thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude and + thing as a force that is not accompanied by an equal and opposite force. In some situations, the magnitude + and direction of the forces are determined entirely by one of the two bodies, say Body A; the force exerted by Body A - on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This law + on Body B is called the "action", and the force exerted by Body B on Body A is called the "reaction". This + law is - sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In other + sometimes referred to as the action-reaction law, with FA called the "action" and FB the "reaction". In + other situations the magnitude and directions of the forces are determined jointly by both bodies and it isn't necessary to identify one force as the "action" and the other as the "reaction". The action and the reaction are - simultaneous, and it does not matter which is called the action and which is called reaction; both forces are + simultaneous, and it does not matter which is called the action and which is called reaction; both forces + are part of a single interaction, and neither force exists without the other.[8] - The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional force + The two forces in Newton's third law are of the same type (e.g., if the road exerts a forward frictional + force on - an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the tires + an accelerating car's tires, then it is also a frictional force that Newton's third law predicts for the + tires pushing backward on the road). - From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, and + From a conceptual standpoint, Newton's third law is seen when a person walks: they push against the floor, + and the floor pushes against the person. Similarly, the tires of a car push against the road while the road pushes back on - the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with the - water, pushing the water backward, while the water simultaneously pushes the person forward—both the person + the tires—the tires and road simultaneously push against each other. In swimming, a person interacts with + the + water, pushing the water backward, while the water simultaneously pushes the person forward—both the + person and - the water push against each other. The reaction forces account for the motion in these examples. These forces - depend on friction; a person or car on ice, for example, may be unable to exert the action force to produce + the water push against each other. The reaction forces account for the motion in these examples. These + forces + depend on friction; a person or car on ice, for example, may be unable to exert the action force to + produce the needed reaction force.[11] @@ -168,51 +188,68 @@

    The Third Law

    particles carry momentum, and in quantum mechanics.

    -

    History

    -

    The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the universe: +

    History

    +

    The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the + universe: that - heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted to be + heavy objects (such as rocks) wanted to be at rest on the Earth and that light objects like smoke wanted + to be at - rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural state + rest in the sky and the stars wanted to remain in the heavens. He thought that a body was in its natural + state when it was at rest, and for the body to move in a straight line at a constant speed an external agent was needed - continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force is + continually to propel it, otherwise it would stop moving. Galileo Galilei, however, realised that a force + is necessary to change the velocity of a body, i.e., acceleration, but no force is needed to maintain its velocity. In other words, Galileo stated that, in the absence of a force, a moving object will continue moving. (The - tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight was + tendency of objects to resist changes in motion was what Johannes Kepler had called inertia.) This insight + was refined by Newton, who made it into his first law, also known as the "law of inertia"—no force means no - acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the law + acceleration, and hence the body will maintain its velocity. As Newton's first law is a restatement of the + law of inertia which Galileo had already described, Newton appropriately gave credit to Galileo.

    -

    Links

    +
    +

      -
    1. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering and +
    2. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering + and science (Series: Schaum's Outline Series). McGraw-Hill Companies. p. 58. ISBN 978-0-07-008498-8.
    3. the Principia on line at Andrew Motte Translation
    4. Andrew Motte translation of Newton's Principia (1687) Axioms or Laws of Motion
    5. Thornton, Marion (2004). Classical dynamics of particles and systems (5th ed.). Brooks/Cole. p. 53. ISBN 978-0-534-40896-1.
      6. -
    6. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for variable - mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. Bibcode:1992CeMDA..53..227P. - doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's second +
    7. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for + variable + mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. + Bibcode:1992CeMDA..53..227P. + doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's + second law is valid for constant mass only. When the mass varies due to accretion or ablation, [an alternate equation explicitly accounting for the changing mass] should be used."
      8. -
    8. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we cannot - derive a general expression for Newton's second law for variable mass systems by treating the mass in F = - dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we apply +
    9. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we + cannot + derive a general expression for Newton's second law for variable mass systems by treating the mass in + F = + dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we + apply it to an entire system of constant mass, having parts among which there is an interchange of mass. [Emphasis as in the original]
      10. -
    10. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. ISBN +
    11. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. + ISBN 978-0-07-035048-9 – via archive.org. Recall that F = dP/dt was established for a system composed of a - certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the time + certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the + time interval[. ...] Consequently, the mass of the system can not change during the time of interest.
    12. Resnick; Halliday; Krane (1992). Physics, Volume 1 (4th ed.). p. 83.
    13. C Hellingman (1992). "Newton's third law revisited". Phys. Educ. 27 (2): 112–115.
      14. -
    14. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is only +
    15. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is + only one aspect of a mutual interaction between two bodies.
    16. Hewitt (2006), p. 75
    17. Newton, Principia, Corollary III to the laws of motion
      18. From a11a3b24f47ca7ec7215f936056dfc3a55d802a6 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Wed, 3 Feb 2021 17:42:28 +0100 Subject: [PATCH 07/13] add footer, fix math img --- css/style.css | 94 ++++++++++-------- index.html | 270 ++++++++++++++++++++++++++------------------------ 2 files changed, 190 insertions(+), 174 deletions(-) diff --git a/css/style.css b/css/style.css index eeef48ea..3235ff55 100644 --- a/css/style.css +++ b/css/style.css @@ -7,37 +7,64 @@ * */ +*, +*:before, +*:after { + -webkit-box-sizing: border-box; + -moz-box-sizing: border-box; + box-sizing: border-box; +} -.header, -.footer { - background-color: grey; - color: white; - padding: 15px; +header, +footer { + background-color: khaki; } h1 { font-size: 300%; text-align: center; + margin-top: 0; } -nav { + +h2 { + margin-top: 2em; + margin-bottom: 3em; +} + +h2, +h3 { + text-align: center; +} + +hr { + margin-top: 3em; +} + + +.math img { display: block; - width: 660px; - margin: 0 auto 30px; + margin: 0 auto; + float: none; + } -body { - margin: 0; +img { + margin: 0 20px 20px 0; + float: right; + } -h2 { - font-family: monospace; - color: #606060; - margin-top: 2em; - margin-bottom: 5em; +main { + + margin: 2em 2em 3em 2em; } -hr { - margin-top: 5em; +article { + font-size: 125%; +} + +article:first-of-type { + font-size: 150%; } ul { @@ -53,7 +80,7 @@ a { nav { display: block; - width: 660px; + width: 490px; margin: 0 auto 30px; } @@ -84,32 +111,15 @@ nav { display: block; } -li { - display: inline; -} - -a { - font-family: 'Lora', serif; - transition: .5s linear; - text-decoration: none; -} - -p { - font-size: 150%; - -} - -.math { - display: inline-block; -} - -img { - float: right; - margin: 20px; +footer { + padding: 1em; + background-color: khaki; + display: flex; + justify-content: space-between; } -main { +footer span { + margin-top: 1em; - margin: 2em 2em 3em 2em; } \ No newline at end of file diff --git a/index.html b/index.html index 3ca75cfc..9285fac4 100644 --- a/index.html +++ b/index.html @@ -7,7 +7,7 @@ - Newton's laws of motion @@ -35,97 +35,98 @@

      Newton's laws of motion

    - - Isaac Newton -

    In classical mechanics, Newton's laws of motion are three laws that describe the relationship - between the motion of an object and the forces acting on it. The first law states that an object - either remains at rest or continues to move at a constant velocity, - unless it is acted upon by an external force. The second law states that the rate of change - f momentum of an object is directly proportional to the force applied, or, for an object with - constant mass, that the net force on an object is equal to the mass of that object multiplied - by the acceleration. The third law states that when one object exerts a force on a second object, - that second object exerts a force that is equal in magnitude and opposite in direction on the first object. - The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia - Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. - Newton used them to explain and investigate the motion of many physical objects and systems, - which laid the foundation for Newtonian mechanics. -

    -
    - -

    The First Law

    -

    The first law states that an object at rest will stay at rest, and an object in motion will - stay in motion unless acted on by a net external force. Mathematically, - this is equivalent to saying that if the net force on an object is zero, - then the velocity of the object is constant.

    - -
    -
    - - -

    Newton's first law is often referred to as the law of inertia. - Newton's first (and second) laws are valid only in an inertial reference frame.[4]

    - -
    -

    The Second Law

    -

    The second law states that the rate of change of momentum of a body over time is directly - proportional to the force applied, and occurs in the same direction as the applied force. - -

    -
    - - -

    Constant Mass

    -

    For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an - object's - acceleration.

    - - -
    -
    - -

    where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the - net - force applied to a body produces a proportional acceleration.

    - -

    Variable-mass systems

    - -

    Variable-mass systems, like a rocket burning fuel and ejecting spent gases, - are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] - The - equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is - obtained - by - applying the second law to the entire, constant-mass system consisting of the body and its ejected or - accreted - mass; - the result is[5]

    +
    + Isaac Newton +

    In classical mechanics, Newton's laws of motion are three laws that describe the relationship + between the motion of an object and the forces acting on it. The first law states that an object + either remains at rest or continues to move at a constant velocity, + unless it is acted upon by an external force. The second law states that the rate of change + f momentum of an object is directly proportional to the force applied, or, for an object with + constant mass, that the net force on an object is equal to the mass of that object multiplied + by the acceleration. The third law states that when one object exerts a force on a second object, + that second object exerts a force that is equal in magnitude and opposite in direction on the first object. +

    +

    + The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia + Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687. + Newton used them to explain and investigate the motion of many physical objects and systems, + which laid the foundation for Newtonian mechanics. +

    +
    +
    +
    +

    The First Law

    +

    The first law states that an object at rest will stay at rest, and an object in motion will + stay in motion unless acted on by a net external force. Mathematically, + this is equivalent to saying that if the net force on an object is zero, + then the velocity of the object is constant.

    + src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cf29dd89fdaf777f52adebc3735e4b63d3ef8810">
    -

    where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation - one - can derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. - Under some conventions, the quantity

    -
    -
    on -

    the - left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on - the - body - by the changing mass, such as rocket - exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the - equation - becomes F = ma. -

    - +

    Newton's first law is often referred to as the law of inertia. + Newton's first (and second) laws are valid only in an inertial reference frame.[4]

    +
    +
    +
    +

    The Second Law

    +

    The second law states that the rate of change of momentum of a body over time is directly + proportional to the force applied, and occurs in the same direction as the applied force. + +

    +
    + + +

    Constant Mass

    +

    For objects and systems with constant mass,[5][6][7] the second law can be re-stated in terms of an + object's + acceleration.

    + + +
    +
    + +

    where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the + net + force applied to a body produces a proportional acceleration.

    + +

    Variable-mass systems

    + +

    Variable-mass systems, like a rocket burning fuel and ejecting spent gases, + are not closed and cannot be directly treated by making mass a function of time in the second law;[6][7] + The + equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is + obtained + by + applying the second law to the entire, constant-mass system consisting of the body and its ejected or + accreted + mass; + the result is[5]

    + +
    +
    + + +

    where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation + one + can derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation. + Under some conventions, the quantity

    +
    +
    +

    on the left-hand side, which represents the advection of momentum, is defined as a force (the force exerted + on the body by the changing mass, such as rocket + exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the + equation becomes F = ma. +

    +
    +

    The Third Law

    The third law states that all forces between two objects exist in equal magnitude and opposite direction: @@ -187,6 +188,8 @@

    The Third Law

    and holds in cases where Newton's third law appears to fail, for instance when force fields as well as particles carry momentum, and in quantum mechanics.

    +
    +

    History

    The ancient Greek philosopher Aristotle had the view that all objects have a natural place in the @@ -211,57 +214,60 @@

    History

    law of inertia which Galileo had already described, Newton appropriately gave credit to Galileo.

    - -
    - -

    -

      -
    1. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering - and - science (Series: Schaum's Outline Series). McGraw-Hill Companies. p. 58. ISBN 978-0-07-008498-8.
      2. -
    2. the Principia on line at Andrew Motte Translation
      3. -
    3. Andrew Motte translation of Newton's Principia (1687) Axioms or Laws of Motion
      4. -
    4. Thornton, Marion (2004). Classical dynamics of particles and systems (5th ed.). Brooks/Cole. p. 53. - ISBN 978-0-534-40896-1.
      5. - -
    5. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for - variable - mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. - Bibcode:1992CeMDA..53..227P. - doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's - second - law is valid for constant mass only. When the mass varies due to accretion or ablation, [an alternate - equation explicitly accounting for the changing mass] should be used."
      6. -
    6. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we - cannot - derive a general expression for Newton's second law for variable mass systems by treating the mass in - F = - dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we - apply - it to an entire system of constant mass, having parts among which there is an interchange of mass. - [Emphasis as in the original]
      7. -
    7. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. - ISBN - 978-0-07-035048-9 – via archive.org. Recall that F = dP/dt was established for a system composed of a - certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the - time - interval[. ...] Consequently, the mass of the system can not change during the time of interest.
      8. -
    8. Resnick; Halliday; Krane (1992). Physics, Volume 1 (4th ed.). p. 83.
      9. -
    9. C Hellingman (1992). "Newton's third law revisited". Phys. Educ. 27 (2): 112–115.
      10. -
    10. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is - only - one aspect of a mutual interaction between two bodies.
      11. -
    11. Hewitt (2006), p. 75
      12. -
    12. Newton, Principia, Corollary III to the laws of motion
      13. - -
    -

    +
    +
    + +

    +

      +
    1. Browne, Michael E. (July 1999). Schaum's outline of theory and problems of physics for engineering + and + science (Series: Schaum's Outline Series). McGraw-Hill Companies. p. 58. ISBN 978-0-07-008498-8.
      2. +
    2. the Principia on line at Andrew Motte Translation
      3. +
    3. Andrew Motte translation of Newton's Principia (1687) Axioms or Laws of Motion
      4. +
    4. Thornton, Marion (2004). Classical dynamics of particles and systems (5th ed.). Brooks/Cole. p. 53. + ISBN 978-0-534-40896-1.
      5. + +
    5. Plastino, Angel R.; Muzzio, Juan C. (1992). "On the use and abuse of Newton's second law for + variable + mass problems". Celestial Mechanics and Dynamical Astronomy. 53 (3): 227–232. + Bibcode:1992CeMDA..53..227P. + doi:10.1007/BF00052611. ISSN 0923-2958. S2CID 122212239. "We may conclude emphasizing that Newton's + second + law is valid for constant mass only. When the mass varies due to accretion or ablation, [an alternate + equation explicitly accounting for the changing mass] should be used."
      6. +
    6. Halliday; Resnick. Physics. 1. p. 199. ISBN 978-0-471-03710-1. It is important to note that we + cannot + derive a general expression for Newton's second law for variable mass systems by treating the mass in + F = + dP/dt = d(M v) as a variable. [...] We can use F = dP/dt to analyze variable mass systems only if we + apply + it to an entire system of constant mass, having parts among which there is an interchange of mass. + [Emphasis as in the original]
      7. +
    7. Kleppner, Daniel; Kolenkow, Robert (1973). An Introduction to Mechanics. McGraw-Hill. pp. 133–134. + ISBN + 978-0-07-035048-9 – via archive.org. Recall that F = dP/dt was established for a system composed of a + certain set of particles[. ... I]t is essential to deal with the same set of particles throughout the + time + interval[. ...] Consequently, the mass of the system can not change during the time of interest.
      8. +
    8. Resnick; Halliday; Krane (1992). Physics, Volume 1 (4th ed.). p. 83.
      9. +
    9. C Hellingman (1992). "Newton's third law revisited". Phys. Educ. 27 (2): 112–115.
      10. +
    10. Resnick & Halliday (1977). Physics (Third ed.). John Wiley & Sons. pp. 78–79. Any single force is + only + one aspect of a mutual interaction between two bodies.
      11. +
    11. Hewitt (2006), p. 75
      12. +
    12. Newton, Principia, Corollary III to the laws of motion
      13. + +
    +

    From e820addeb666a5cf70221ebdae82619bd269554a Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Wed, 3 Feb 2021 18:11:44 +0100 Subject: [PATCH 08/13] small fix --- css/style.css | 1 + index.html | 1 + 2 files changed, 2 insertions(+) diff --git a/css/style.css b/css/style.css index 3235ff55..93ad05e3 100644 --- a/css/style.css +++ b/css/style.css @@ -7,6 +7,7 @@ * */ + *, *:before, *:after { diff --git a/index.html b/index.html index 9285fac4..bb80d2e4 100644 --- a/index.html +++ b/index.html @@ -35,6 +35,7 @@

    Newton's laws of motion

+
Isaac Newton From c820cdcafbe659bb266e9c8be13fea8ace06c4d0 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Thu, 4 Feb 2021 00:39:20 +0100 Subject: [PATCH 09/13] fix nav --- css/style.css | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/css/style.css b/css/style.css index 93ad05e3..79006823 100644 --- a/css/style.css +++ b/css/style.css @@ -81,7 +81,7 @@ a { nav { display: block; - width: 490px; + width: 90%; margin: 0 auto 30px; } From 705f5fae8949e4bfd447c91fb9814bf586eef4cc Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Thu, 4 Feb 2021 00:44:41 +0100 Subject: [PATCH 10/13] fix nav flex --- css/style.css | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/css/style.css b/css/style.css index 79006823..e43f7c97 100644 --- a/css/style.css +++ b/css/style.css @@ -81,7 +81,7 @@ a { nav { display: block; - width: 90%; + margin: 0 auto 30px; } @@ -95,6 +95,7 @@ nav { background: rgba(177, 152, 145, .3); border-right: 1px solid #b19891; color: #695753; + width: 12%; } .one a:hover { @@ -103,13 +104,16 @@ nav { .one li { display: inline; + } .one ul { list-style: none; margin: 0; padding-left: 0; - display: block; + display: flex; + justify-content: space-between; + } From fd796f8cede8d712ed392fb4c7e4416cf95aef53 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Thu, 4 Feb 2021 00:55:29 +0100 Subject: [PATCH 11/13] fix menu --- css/style.css | 26 +++++++++++++------------- 1 file changed, 13 insertions(+), 13 deletions(-) diff --git a/css/style.css b/css/style.css index e43f7c97..0db3520e 100644 --- a/css/style.css +++ b/css/style.css @@ -7,7 +7,7 @@ * */ - + *, *:before, *:after { @@ -22,7 +22,7 @@ footer { } h1 { - font-size: 300%; + font-size: 250%; text-align: center; margin-top: 0; } @@ -50,7 +50,7 @@ hr { } img { - margin: 0 20px 20px 0; + margin: 0 0 20px 20px; float: right; } @@ -74,37 +74,37 @@ ul { } a { - text-decoration: none; + /* text-decoration: none; */ font-family: 'Lora', serif; - transition: .5s linear; + transition: .25s linear; } nav { display: block; + - margin: 0 auto 30px; } .one ul { - padding: 1em 0; + padding: 0.75em 0; background: #ECDAD6; } .one a { - padding: 1em; - background: rgba(177, 152, 145, .3); + /* padding: 0 auto; */ + /* background: rgba(177, 152, 145, .3); */ border-right: 1px solid #b19891; color: #695753; - width: 12%; + /* width: 15%; */ } .one a:hover { - background: #b19891; + /* background: #b19891; */ } .one li { display: inline; - + } .one ul { @@ -113,7 +113,7 @@ nav { padding-left: 0; display: flex; justify-content: space-between; - + } From e59afcf2f8edacaeb3a7643e9e7623a041dc8f63 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Thu, 4 Feb 2021 01:01:04 +0100 Subject: [PATCH 12/13] text word-break on --- css/style.css | 4 ++++ index.html | 2 +- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/css/style.css b/css/style.css index 0db3520e..1ae17993 100644 --- a/css/style.css +++ b/css/style.css @@ -79,6 +79,10 @@ a { transition: .25s linear; } +p { + word-break: break-all; +} + nav { display: block; diff --git a/index.html b/index.html index bb80d2e4..c3fa8687 100644 --- a/index.html +++ b/index.html @@ -38,7 +38,7 @@

Newton's laws of motion

Isaac Newton + alt="Isaac Newton" height="270px">

In classical mechanics, Newton's laws of motion are three laws that describe the relationship between the motion of an object and the forces acting on it. The first law states that an object either remains at rest or continues to move at a constant velocity, From 778a30897009b92ad7e92a82d831af55d5240025 Mon Sep 17 00:00:00 2001 From: ArthurNNN Date: Thu, 4 Feb 2021 01:05:01 +0100 Subject: [PATCH 13/13] css optimize --- css/style.css | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/css/style.css b/css/style.css index 1ae17993..32bfc352 100644 --- a/css/style.css +++ b/css/style.css @@ -86,7 +86,7 @@ p { nav { display: block; - + } .one ul { @@ -95,15 +95,8 @@ nav { } .one a { - /* padding: 0 auto; */ - /* background: rgba(177, 152, 145, .3); */ - border-right: 1px solid #b19891; + margin: 1em; color: #695753; - /* width: 15%; */ -} - -.one a:hover { - /* background: #b19891; */ } .one li {