An ice skater is going to execute a triple axel jump (three full rotations in th

Question

An ice skater is going to execute a triple axel jump (three full rotations in the air). He spends 0.95 s in the air for this jump, his mass is 70 kg, and his average radius of gyration about the vertical axis while airborne is 18 cm. Assume that he remains vertical throughout the jump. Before starting his set-up for the jump, he is skating in a straight line. The set-up lasts 0.35 s and at the end of the set-up his skates leave the ice. What average moment does the ice exert on him during the set-up? Notice that there is no moment acting on him while he is in the air, so his angular acceleration while airborne is zero.

Possible relevant equations:

Mass moment of inertia:

Area moment of inertia:

L(angular momentum) = I * w(angular velocity)

Explanation / Answer

Moment Exerted is M = Force*Time

Force is rate of change of angular momentum = L/Time

L is given by

L = I * w(angular velocity)

L = 0.5*m*r^2 * w

L = 0.5*70*0.18^2 *3/ 0.95

L = 3.58

Force = L/ Time = 3.58/0.35 sec

Moment Exerted = Force*Time = 3.58 N/s

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