Part A A 45 kg figure skater is spinning on the toes of her skates at 0.80 rev/s

Question

Part A A 45 kg figure skater is spinning on the toes of her skates at 0.80 rev/s Her arms are outstretched as far as they will go. In this orientation, the skater can be modeled as a cylindrical torso (40 kg. 20 cm average diameter, 160 cm tall) plus two rod- like arms (2.5 kg each, 71 cm long) attached to the outside of the torso. The skater then raises her arms straight above her head, where she appears to be a 45 kg 20-cm-diameter, 200-cm-tall cylinder What is her new rotation frequency, in revolutions per second? Express your answer to two significant figures and include the appropriate units. 6.17 rev Submit My Answers Give Up Incorrect; Try Again; 3 attempts remaining Provide Feedha

Explanation / Answer

initial moment of inertia I1 = (1/2)*mc*r1^2 + 2*(1/12)*mara*L^2 + 2*marm*(L/2+r1)^2

I1 = (1/2)*40*0.1^2 + 2*((1/12)*2.5*0.71^2)+(2*2.5*(0.71/2+0.1)^2)

I1 = 1.445 kg m^2

initial angular momentum Li = I1*w1

after raising the hands

final moment of inertia I2 = (1/2)*Mc*r2^2 = (1/2)*45*0.1^2 = 0.225 kg m^2

final angular moemntum Lf = I2*w2

from conservation of angular momentum Lf = Li

0.225*w2 = 1.445*0.8

w2 = 5.14 rev/s <<<---ANSWER

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