I think I'm not understanding something about this problem. Can someone help me out?(adsbygoogle = window.adsbygoogle || []).push({});

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

A 2.0 kg disk traveling a 3.0 m/s strikes a 1.0 kg stick of length 4.0 m that is lying flat on nearly frictionless ice. The disk strikes the endpoint of the stick, at a distance r = 2.0 m from the stick's center. Suppose the collision is perfectly inelastic so that the disk adheres to the stick at the endpoint at which it strikes. The moment of inertia of the stick about its center of mass is 1.33 kg*m^{2}. Find the angular speed of the system after the collision.

2. Relevant equations

(I think) Parallel axis theorem: I= Icm + mr^{2}

L= r cross p

L= I*omega

m= mass disk

3. The attempt at a solution

L = L'

r cross p = I(system)*omega

mvr = (I(stick) + I(disk) + mvr^{2})*omega

mvr = (I(stick) + (1/2)mr^{2}+ mr^{2})*omega

omega = mvr/(I(stick) + 2/3(mr^{2}))

omega = 2.0kg(3.0m/s)(2.0m)/(1.33kg*m^{2}+1.5(2.0kg)(2.0m)^{2})

omega= .90 rad/s

The answer is 1.0 rad/s.

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# Homework Help: Perfectly Inelastic Disk and Stick Collision- Angular Speed

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