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-   -   Proving Rotational K.E. Formula? (http://www.physicsforums.com/showthread.php?t=656227)

greswd Dec2-12 02:54 AM

Proving Rotational K.E. Formula?
 
The total kinetic energy (as viewed from one inertial frame) of a free, rigid body is the sum of all the infinitesimal kinetic energies of the components that comprise the body.


How do we prove that for a rotating body

[tex]E_k=\frac{1}{2}\left(M_{T} v_{c}^{2} + I_{c} ω^{2}\right)[/tex]

greswd Dec2-12 07:52 AM

Re: Proving Rotational K.E. Formula?
 
Where MT stands for the total mass of all the infinitesmal components combined.

mfb Dec2-12 08:25 AM

Re: Proving Rotational K.E. Formula?
 
Integrate ##\int \frac{1}{2}v^2 \rho dV## (in other words, kinetic energy = 1/2m^2 for all infinitesimal m) and split v into components from translation and rotation and you will get the correct result.


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