Function to return Total Energy in physics/mechanics #16202

ritesh99rakesh · 2019-03-08T10:33:16Z

Brief description of what is fixed or changed

At present, we have function to get the kinetic energy and potential energy of rigid body, but we do not have any function to give the total energy of the rigid body. This PR adds a function under sympy/physics/mechanics/rigidbody.py to return the total energy of the body.
I have defined total_energy = kinetic_energy + potential_energy

Other comments

Please review it and comment your suggestions.

Release Notes

physics.mechanics
- added functions total_energy, rotational_kinetic_energy, and translational_kinetic_energy, in rigidbody.py
- added function total_energy in particle.py

sympy-bot · 2019-03-08T10:33:28Z

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physics.mechanics
- added functions total_energy, rotational_kinetic_energy, and translational_kinetic_energy, in rigidbody.py (#16202 by @ritesh99rakesh)
- added function total_energy in particle.py (#16202 by @ritesh99rakesh)

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<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->
Fixes #16201 

#### Brief description of what is fixed or changed
At present, we have function to get the kinetic energy and potential energy of rigid body, but we do not have any function to give the total energy of the rigid body. This PR adds a function under ```sympy/physics/mechanics/rigidbody.py``` to return the total energy of the body. 
I have defined total_energy = kinetic_energy + potential_energy

#### Other comments
Please review it and comment your suggestions.

#### Release Notes

<!-- Write the release notes for this release below. See
https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more information
on how to write release notes. The bot will check your release notes
automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
* physics.mechanics
    * added functions total_energy, rotational_kinetic_energy, and translational_kinetic_energy, in rigidbody.py
    * added function total_energy in particle.py


<!-- END RELEASE NOTES -->

…ticle.py and better comment in rigidbody.py for total_energy

codecov · 2019-03-08T12:04:34Z

Codecov Report

Merging #16202 into master will increase coverage by 0.123%.
The diff coverage is 100%.

@@              Coverage Diff              @@
##            master    #16202       +/-   ##
=============================================
+ Coverage   73.596%   73.719%   +0.123%     
=============================================
  Files          618       619        +1     
  Lines       158481    158455       -26     
  Branches     37187     37134       -53     
=============================================
+ Hits        116636    116813      +177     
+ Misses       36417     36219      -198     
+ Partials      5428      5423        -5

shiksha11 · 2019-03-10T07:28:14Z

Why in the total energy expression roatational kinetic energy is not I*(w**2)/2 ?

ritesh99rakesh · 2019-03-10T18:28:17Z

Why in the total energy expression roatational kinetic energy is not I*(w**2)/2 ?

Also I had the same doubt but it is due to the function which calculates the I and we get the expression for rotational kinetic energy as (w**2)/2

ritesh99rakesh · 2019-03-10T18:31:06Z

I have added new functions rotational_kinetic_energy and translational_kinetic_energy which will the return the rotational and translational component of kinetic energy, repectively. Please let me know if these are needed or should I remove these. Ping @moorepants, @oscargus .

oscargus · 2019-03-16T23:43:13Z

I do not know much about the physics module so there are others who are more suitable to review the functionality.

sympy/physics/mechanics/rigidbody.py

smichr · 2019-03-17T13:45:54Z

please add release notes, too

ritesh99rakesh · 2019-03-17T14:06:33Z

Thank you for your reply @smichr. Also what exactly do I have to write in release notes?

smichr · 2019-03-19T01:14:06Z

👓 See this for more information
on how to write release notes. for suggestions on release notes. You added new functions. someone reading the release notes will be interested.

sympy/physics/mechanics/tests/test_particle.py

ritesh99rakesh · 2019-03-19T07:25:34Z

@smichr I have added release notes, please reivew them. Regards.

oscargus · 2019-03-19T11:52:20Z

I think something like:
added functions total_energy, rotational_kinetic_energy, and translational_kinetic_energy, in rigidbody.py
added function total_energy in particle.py

would do.

ritesh99rakesh · 2019-03-20T15:23:42Z

If this PR looks fine, please merge it. Ping @oscargus, @smichr

ritesh99rakesh · 2019-04-01T19:30:57Z

@oscargus could you guide me what has to be done to complete this PR?

sympy/physics/mechanics/tests/test_particle.py

sympy/physics/mechanics/rigidbody.py

moorepants · 2019-04-01T19:44:45Z

sympy/physics/mechanics/rigidbody.py

+        >>> B.total_energy(N)
+        M*g*h + M*v**2/2 + omega**2/2
+        """
+        return self.kinetic_energy(frame) + self.potential_energy


This should raise an error if potential energy is not defined.

moorepants · 2019-04-01T19:45:50Z

sympy/physics/mechanics/particle.py

+        g*h*m + m*v**2/2
+
+        """
+        return self.kinetic_energy(frame) + self.potential_energy


Should raise an error if potential_energy is not defined.

At present, potential_energy for a body for which potential_energy is not explicitly defined is taken as zero. I think this makes sense. What do you think about it?

It is a bit misleading. If I type "total_energy" I'm expecting to get KE + PE, but if PE is zero by default I'm not getting any PE contribution. I feel like it would be best to inform the user that they aren't getting what they ask for. Maybe a warning message that tells the user that PE is zero and not set is sufficient.

moorepants · 2019-04-01T19:46:09Z

This looks useful, I've provided some comments.

ritesh99rakesh · 2019-04-03T17:25:22Z

@moorepants please review the changes.

moorepants · 2019-04-03T21:32:36Z

If you add warnings when PE is zero for the total_energy functions then it LGTM.

ritesh99rakesh · 2019-05-15T07:24:25Z

If you add warnings when PE is zero for the total_energy functions then it LGTM.

@moorepants I was trying to complete this PR. I have the following

>>> from sympy.physics.mechanics import RigidBody, Point, outer, ReferenceFrame
>>> from sympy import symbols
>>> M, g, h = symbols('M g h')
>>> b = ReferenceFrame('b')
>>> P = Point('P')
>>> I = outer (b.x, b.x)
>>> Inertia_tuple = (I, P)
>>> B = RigidBody('B', P, b, M, Inertia_tuple)
>>> B.potential_energy
0
>>> B.potential_energy = 0
>>> B.potential_energy
0

Therefore, in both cases when potential_energy is not set and when potential_energy is set to zero, the output is same. So, how would I distinguish between both?
Ping @smichr

czgdp1807 · 2019-12-19T06:41:26Z

@ritesh99rakesh Would you like to complete this PR?

czgdp1807 · 2020-03-05T09:24:25Z

IMO, K.E. + P.E. is total mechanical energy, so the name should be changed accordingly.
Looks like a nice addition.

ritesh99rakesh · 2020-03-12T06:24:18Z

Closed in favour of #18838

ritesh99rakesh added 2 commits March 8, 2019 13:54

added total_energy

316b6fc

added total_energy and test for total_energy

b0f4cde

added total_energy for Particle, test for total_energy under test_par…

cf1ca7e

…ticle.py and better comment in rigidbody.py for total_energy

ritesh99rakesh added 2 commits March 8, 2019 17:37

removed trailing white spaces

18fc488

corrected test error

b30f11f

oscarbenjamin added the physics.mechanics label Mar 8, 2019

Merge branch 'master' into 16201

90db23b

ritesh99rakesh added 2 commits March 10, 2019 23:19

Merge branch 'master' into 16201

16f2078

added functions for rotational and translational kinetic energy

9d3db99

corrected example under translational_kinetic_energy

0fd70ac

smichr reviewed Mar 17, 2019

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sympy/physics/mechanics/rigidbody.py Outdated Show resolved Hide resolved

made typo correction

b272238

oscarbenjamin reviewed Mar 19, 2019

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sympy/physics/mechanics/tests/test_particle.py Outdated Show resolved Hide resolved

corrected test for total_energy and kinetic_energy

ec6c9c6

Merge branch 'master' of https://github.com/sympy/sympy into 16201

1960c3d

moorepants reviewed Apr 1, 2019

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moorepants reviewed Apr 1, 2019

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moorepants reviewed Apr 1, 2019

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sympy/physics/mechanics/rigidbody.py Show resolved Hide resolved

moorepants reviewed Apr 1, 2019

View reviewed changes

replace & with dot()

158f574

czgdp1807 added the Please take over label Mar 5, 2020

ritesh99rakesh mentioned this pull request Mar 12, 2020

Function to return Total Energy in physics/mechanics #18838

Closed

ritesh99rakesh closed this Mar 12, 2020

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Function to return Total Energy in physics/mechanics #16202

Function to return Total Energy in physics/mechanics #16202

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Function to return Total Energy in physics/mechanics #16202

Function to return Total Energy in physics/mechanics #16202

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ritesh99rakesh commented Mar 8, 2019 • edited

Brief description of what is fixed or changed

Other comments

Release Notes

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Codecov Report

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