A student holds two leadweights, each ofmass 11 kg. When the students’arms are e

Question

A student holds two leadweights, each ofmass

11 kg. When the students’arms are extended

horizontally, the lead weightsare 0.98 m from

the axis of rotation and thestudent rotates

with an angular speed of1.9rad/sec. The

moment of inertia of studentplus stool is

5.5 kgm2 and is assumed to be constant; i.e.,

the student’s arms are massless! Thenthe

student pulls the lead weightshorizontally to

a radius 0.22 m from the axis ofrotation.

Calculate the final angularspeed of the

system. Answer in units ofrad/s.

Explanation / Answer

we know that Iw(i.e. angular momentum) is conserved so m1r21w1 = m1r22w2 so here, moment of inertia of system is given by:: body + lead weights = 5.5 + 2*11*r2 so , now putting the values we get: (5.5 + 2*11*0.982)*1.9 =( 5.5 +2*11*0.222)*x so x= 4.05 rad /s

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