Physics
posted by Tarren .
A skater spinning with angular speed of 1.5 rad/s draws in her outstretched arms thereby reducing her moment of inertia by a factor a 3.
a) Find her angular speed.
b)What is the ratio of her final angular momentum to her initial angular momentum?
c)Did her mechanical energy change? (Yes but why?)

I forgot to add one more part.
d) Determine the ratio of her final kinetic energy to her initial kinetic energy. 
I*w stays the same due to the requirement for angular momentum conservation.
If I is cut in half, w must double.
KE is (1/2)I*w^2 = (1/2)(I*w)^2/I
Since I drops by half while I*w is constant, the kinetic energy must also double.
The extra KE comes from work done by the skater pulling in her arms. There is a lot of centrifugal resistance.
Respond to this Question
Similar Questions

Physics
A woman stands at the center of a platform. The woman and the platform rotate with an angular speed of 4.00 rad/s. Friction is negligible. Her arms are outstreched, and she is holding a dumbbell in each hand. In this position the total … 
ice skater world problem
A skater spins with an angular speed of 12.4 rad/s with her arms outstretched. She lowers her arms, decreasing her moment of inertia by a factor of 8.00. Ignoring friction on the skates, what will be the skater's final angular speed? 
physics
A skater spinning with angular speed of 1.5 rad/s draws in her outstretched arms thereby reducing her moment of inertia by a factor a 3. a) Find her final angular speed. b)What is the ratio of her final angular momentum to her initial … 
physics
An ice skater has a moment of inertia of 2.3 kg * m^2 when his arms are outstretched and a moment of inertia of 1.0 kg * m^2 when his arms are tucked in close to his chest. If he starts to spin at an angular speed of 2.0 rps (revolutions … 
Physics
A figure skater is spinning with an initial angular speed of 6.9rad/s. She then pulls her arms in, reducing her moment of inertia to 0.38 times its original value. What is her angular speed after pulling in her arms? 
physics
(a) Calculate the angular momentum of an ice skater spinning at 6.00 rev/s given his moment of inertia is 0.490 kg·m2. (b) He reduces his rate of spin (his angular velocity) by extending his arms and increasing his moment of inertia. … 
Physics
A 5.0 kg skater begins a spin with an angular speed of 4 rad/s. By changing the position of her arms, the skater decreases her moment of inertia to one half its initial value. What is the skater's final angular speed? 
Physics
A 5.0 kg skater begins a spin with an angular speed of 4 rad/s. By changing the position of her arms, the skater decreases her moment of inertia to one half its initial value. What is the skater's final angular speed? 
Physics
A figure skater is spinning with an initial angular speed of 5.6rad/s. He then pulls his arms in, reducing his moment of inertia to 0.31 times its original value. What is his angular speed after pulling in his arms? 
physic
a skater with moment of inertia 15 kgm2 begins a spin with an angular speed of 6.0 rad/s by changing the position of her arms, the skater decreases her moment of inertia by 50% what is the skaters final angular speed