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The first question asks what happens when her moment of inertia increases, not decreases and I have been having issues with this. The second question, I keep coming up with 64. Can anyone help me with these two?

An ice skater stars a spin with her arms stretched out of the sides. She balances on the tip of one skate to turn without friction. She then pulls her arms in so that her moment of inertia increases by a factor of 2. In the process of her doing so, what happens to her kinetic energy?

 A.It remains constant.   
 B.It decreases by a factor of 4.   
 C.It decreases by a factor of 2.   
 D.It increases by a factor of 4.   
 E.It increases by a factor of 2.


A certain light truck can go around a curve having a radius of 150 m with a maximum speed of 32 m/s. To have the same acceleration, at what maximum speed can it go around a curve having a radius of 600 m?
 A.32 m/s   
 B.45 m/s   
 C.16 m/s   
 D.23 m/s   
 E.75 m/s   

Remember the equation for centripetal acceleration,

a = v²/r. Now notice that the radius is half as much, so to keep a the same, v² will also have to be half as much.

If v = 37, v² = 1369. But if the radius is half as much, to keep a the same, v² would need to be 1369/2 = 684.5, and taking the square root gives v = 26.2 m/s.

So its maximum speed on a curve of radius 140 m is 26.2 m/s

Answer provided in the attachment below.