# how to calculate rotational energy of particle

hello

i am simulating a particle column collapse, the particle system is consist of sphere and polyhedra, and i want calculate the energy loss caused by friction and the kinetic energy, so i need to know how to calculate the rotational energy, can you give me some advice, lookforward for your answer

## Question information

- Language:
- English Edit question

- Status:
- Answered

- For:
- Yade Edit question

- Assignee:
- No assignee Edit question

- Last query:
- 2019-08-21

- Last reply:
- 2019-08-21

lip (mr.xie) said : | #1 |

by the way, i know that function yade._utils.

become useless to me, can you give me some advice?

Jan Stránský (honzik) said : | #2 |

> which will make the function yade._utils.

I would not be that strict.

Even I dare to say that the implementation of kineticEnergy(), namely formulas for linear kinetic energy [1], rotational kinetic energy of spherical particle [2] and rotational kinetic energy of aspherical particle [3] could be actually very useful :-)

cheers

Jan

[1] https:/

[2] https:/

[3] https:/

lip (mr.xie) said : | #3 |

dear Jan:

thanks for your answer. i noticed that the code below might solve my problem:

Matrix3r T(state->ori);

// the tensorial expression http://

// inertia tensor rotation from http://

Matrix3r mI; mI<<state-

//E+

E+=.

}

but i still have a problem, i think the code 'Matrix3r T(state->ori)' is used to conver quaternionr into a rotating matrix,if so, how can i achieve that by python? can you give me some advice?

Jan Stránský (honzik) said : | #4 |

b.state.

hint:

b = sphere((0,0,0),1)

help(b.state.ori)

cheers

Jan

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