A student sits on a rotating stool holding two 3.4-kg objects. When his arms are
ID: 1478328 • Letter: A
Question
A student sits on a rotating stool holding two 3.4-kg objects. When his arms are extended horizontally, the objects are 1.0 m from the axis of rotation and he rotates with an angular speed of 0.75 rad/s. The moment of inertia of the student plus stool is 3.0 kg · m2 and assumed to be constant. The student then pulls in the objects horizontally to 0.29 m from the rotation axis.
(a) Find the new angular speed of the student. _____ rad/s
(b) Find the kinetic energy of the student before and after the objects are pulled in.
before ____ J after ______ JExplanation / Answer
where angularar momentum is constant
so Iw=constant
I1w1=constant
I1w1=I2W2
w2=I1w1/I2
calculated I1 =3+2*3.14*1^2
=9.8kgm^2
same calculatedI2 =4.50kgm2
w2=0.75*9.8/4.5
=1.63rad/sec
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