# How we can find the kinetic energy? [closed]

A solid disk of mass m is rolling along a surface its center has velocity v what is the kinetic energy of disk?I cannot solve the problem,

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## closed as too localized by David Z♦Jul 13 '12 at 15:50

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Hi Zeyneb, and welcome to Physics Stack Exchange! This is a site for conceptual questions about physics, not general homework help. If you can edit your question to ask about the specific physics concept that is giving you trouble, I'll be happy to reopen it. See our FAQ and homework policy for more information. –  David Z Jul 13 '12 at 15:50

the rules forbid us from answering homework questions, but we're allowed to discuss the concepts involved.

In your case the disk has energy because it's moving at velocity $v$, and you calculate the kinetic energy in the usual way for a moving body. It also has energy because it's rotation. You know the speed of the edge of the disk (assuming it's not skidding as the disk rotates) so you can work out it's energy of rotation. If you don't know the equation for calculkating the rotational energy of a disk it's easily Googled for.

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$E_{k}= \frac{1}{2}mv^{2} + \frac{1}{2}I \omega ^{2}$

the first term is because the disk is rolling

the second term is due to its rotational energy..

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