A student sits on a rotating stool holding two 4 kg objects. When his arms are e
ID: 2148681 • Letter: A
Question
A student sits on a rotating stool holding two 4 kg objects. When his arms are extended horizontally, the objects are 0.8 m from the axis of rotation, and he rotates with angular speed of 0.74 rad/sec. The moment of iner- tia of the student plus the stool is 6 kgm2 and is assumed to be constant. The student then pulls the objects horizontally to a radius 0.32 m from the rotation axis.
a) Calculate the final angular speed of the student. Answer in units of rad/s
b) Calculate the change in kinetic energy of the system. Answer in units of J
Explanation / Answer
I1=6+2*4*0.82=11.12kgm2
I2=6+2*4*0.322=6.82kgm2
Final angular velocity=I11/I2=1.21 rad/s
b)KE=0.5(6.82*1.212-11.12*0.742)=1.92J
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