# Homework Help: Rotational Motion Around Two Cylinders

1. Mar 4, 2013

### lila.haj

1. The problem statement, all variables and given/known data

The ropes in the figure are each wrapped around a cylinder, and the two cylinders are fastened together. The smaller cylinder has a diameter of 10 cm and a mass of 5.0 kg; the larger cylinder has a diameter of 20 cm and a mass of 20 kg. What is the angular acceleration of the cylinders? Assume that the cylinders turn on a frictionless axle. I know the answer is 3.5 rad/s2.

Figure: http://session.masteringphysics.com/problemAsset/1176936/5/P7-59.jpg

2. Relevant equations

$\alpha$=τ/I
τ=rF
I=1/2*M*R2

3. The attempt at a solution

I tried calculating the net torque of the cylinders caused by the hanging masses. I then divided the net torque by the total inertia on the cylinders using the first equation listed above.

Last edited: Mar 4, 2013
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