PHYSICS 1
posted by kelsey on .
When a pitcher throws a curve ball, the ball is given a fairly rapid spin. A 0.15 kg baseball with a radius of 3.7 cm is thrown with a linear speed of 41 m/s and an angular speed of 37 rad/s. Assume that the ball is a uniform, solid sphere.
(b) Calculate how much of its kinetic energy is rotational.
rotational is 1/2 I w^2 yes?
I of sphere is 2/5mr^2 yes?
so would it not be 1/2[(2/5 X .15 X .037^2) X (41/.037)^2]
please help!

"Yes" to your first two questions.
You used a wrong number for the angular speed w. It is 37 rad/s, as stated.
You only use the relation w = V/R for rolling objects (cylinders and spheres)that are not slipping
The speed of the ball, V = 41 m/s, has nothing to do with the rotational kinetic energy 
thank you so much! i figured it out!

My pleasure and congratulations! It is great to help students who show their work