A student sits on arotating stool holding two 2kg objects. When his arms are ext
ID: 1755142 • Letter: A
Question
A student sits on arotating stool holding two 2kg objects. When his arms are extendedhorizontally, the objects are 1m apart from the axis of rotation,and he rotates with angular speed of 0.66 rad/sec. The moment ofinertia of the student plus the stool is 3kgm2 and isassumed to be constant. The student then pulls the objectshorizontally to a radius 0.35m from the rotation axis.
a) calculate the finalangular speed of the student (answer in units of rad/s)
b)Calculate the change in kinetic energy of the system. (answer inunits of J)
Explanation / Answer
since angular momentum is conserved, initial angular momentum = final ang. momentum initial I = 3 + (2)(1)2 = 5 initial angular velocity = .66 final I = 3 + (2)(.35)2 = 3.245 initial angular velocity = 3.245 = 5(.66) = 3.3 = 1.02 rad/s change in KE = final KE - initial KE =(1/2)(3.245)(1.02)2 - (1/2)(5)(.66)2 = .6 J hope this helps!
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