# Physics

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A 15 kg uniform disk of radius R = 0.25 m has a string wrapped around it, and a m = 3.3 kg weight is hanging on the string. The system of the weight and disk is released from rest.

When the 3.3 kg weight is moving with a speed of 2.1 m/s, what is the kinetic energy of the entire system?

• Physics - ,

This isn't my work, so no credit goes to me. Also, we're probably in the same class.

"Remember that a = αR, or α = a/R

Solve for acceleration by using vf2=vi2+2ax (vf=2.2, vi=0, x=(answer in part b))
That gives you the linear a… we want angular acceleration so we just divide our linear acceleration by the radius:

((2.1)^2)/(2*0.5*(2.1^2)*(3.3+(.5*15))/(3.3*9.8))/0.25

= 11.978"

• Physics - ,

No, we probably aren't in the same class. I take that back. However, my answer should still be right. It should be in rad/s^2 though: 11.978 rad/s^2

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