Question

a figure skater presses off the ice to begin spinning with her arms close to her body. after completing 2 turns in 0.8 seconds she moves her arms further away from her body, what will her new angular velocity be?

a. <16.6rad/s

b. 18 rad/s

c. 20 rad/s

d. 24 rad/s

Answer 1

Let the moment of inertia before she move her hands away is I1​​​​​​

And the moment of inertia after she move her hands away is I2​​​​​​

As we know that when her hands move away from the axis of rotation the distance of mass is increase due this moment of inertia is also increase so,

I2 > I1

Now, it is given that it complete 2 turns in 0.8 sec so,

By angular momentum conservation :

As per given condition :

Answer (a)