A student sits on a rotating stool holding two 2.2-kg objects. When his arms are

Question

A student sits on a rotating stool holding two 2.2-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 is assumed to be constant. The student then pulls in the objects horizontally to 0.28 m from the rotation axis. (a) Find the new angular speed of the student. Correct: Your answer is correct. rad/s (b) Find the kinetic energy of the student before and after the objects are pulled in. before Incorrect: Your answer is incorrect. Your response differs from the correct answer by more than 10%. Double check your calculations. J after Incorrect: Your answer is incorrect. Your response differs from the correct answer by more than 100%. J

Explanation / Answer

I know you already have part A correct, bu t I have to resolve it to get part B

Part A)

Iw = Iw

[(3 + 2(2.2)(12)](.75) = [(3 + 2(2.2)(.28)2](w)

5.55 = 3.34w

w = 1.66 rad/s

KE initial = .5Iw2

KE = .5[(3 + 2(2.2)(1)](.75)2 = 2.08 J

KE final...

KE final = .5[(3 + 2(2.2)(.28)2](1.66)2

KE final = 4.61 J

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