Question
Asked Oct 17, 2019
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Answer the following questions:
a) Explain how skaters can quickly go from a slow to fast spin and vice versa.
b) What happens to their angular velocity and moment of inertia?
c) Is an external torque required? Explain

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Expert Answer

Step 1
a) Momentum is dependent on the speed of rotation and the distance from the centre of
mass
The product of the skater's angular spin rate and moment of inertia is the angular
momentum. That angular momentum remains nearly constant except for a slow
decrease due to the low amount of blade friction on the ice. The moment of inertia is a
measure ofhow much ofthe skater's mass is located for from the spin axis
If a skater spins with their arms out and then brings their arms in, the distance from
the centre is reduced and they spin faster - this maintains their total momentum. Then,
if they put their arms out again they will slow down. The only extemal force involved
in a skater's spin is friction - with the ice and with the air
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a) Momentum is dependent on the speed of rotation and the distance from the centre of mass The product of the skater's angular spin rate and moment of inertia is the angular momentum. That angular momentum remains nearly constant except for a slow decrease due to the low amount of blade friction on the ice. The moment of inertia is a measure ofhow much ofthe skater's mass is located for from the spin axis If a skater spins with their arms out and then brings their arms in, the distance from the centre is reduced and they spin faster - this maintains their total momentum. Then, if they put their arms out again they will slow down. The only extemal force involved in a skater's spin is friction - with the ice and with the air

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Step 2
b) Angular momentum goes up and momentum of inertia goes down
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b) Angular momentum goes up and momentum of inertia goes down

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Science

Physics

Angular Motion

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