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find the speed of the ball's center of mass vCM at the time pure rolling motion occurs.

i used (1/2)mvo^2=(1/2)mVCM^2 + (1/2)Iw^2

I=(2/5)mr^2

i got vo^2=(7/5)v^2 which is wrong.

how do i solve this problem?

- Thread starter Xamfy19
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- #1

- 60

- 0

find the speed of the ball's center of mass vCM at the time pure rolling motion occurs.

i used (1/2)mvo^2=(1/2)mVCM^2 + (1/2)Iw^2

I=(2/5)mr^2

i got vo^2=(7/5)v^2 which is wrong.

how do i solve this problem?

- #2

Doc Al

Mentor

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It looks like you are assuming that energy is conserved. Why?Originally posted by Xamfy19

i used (1/2)mvo^2=(1/2)mVCM^2 + (1/2)Iw^2

I=(2/5)mr^2

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- #4

Doc Al

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Picture what's happening. The ball starts with pure translational motion. The friction slows the translational motion, and starts the ball rotating. So write equations for the translational motion and for the rotational motion, due to the friction. The ball will slow down (but increase rotational speed) until the speed is just right to stop slipping.

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