A 45kg figure skater is spinning on the toes of her skates at 0.60rev/s . Her ar

Question

A 45kg figure skater is spinning on the toes of her skates at 0.60rev/s . Her arms are outstretched as far as they will go. In this orientation, the skater can be modeled as a cylindrical torso (40kg , 20 cm average diameter, 160 cm tall) plus two rod-like arms (2.5kg each, 65cm 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 cylinde

What is her new rotation frequency, in revolutions per second?

Explanation / Answer

By the coservation of angular momentum

I1 w1 = I2 w2

w2 =w1( I1 / I2).........1

I1= 0.5(40)(0.1)2 + 2(2.5)(0.64)2 / 12 + 0.422

I1= 0.54kg.m2

I2 = 0.5(45)(0.1)2 = 0.225

putting the values of I1 and I2 in eq1

w2 = 0.60 rev/s( 0.54/0.225)

       = 1.47rev/s

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