Homework Help: PHYSICS 1

Posted by kelsey on Monday, October 20, 2008 at 4:28am.

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!

PHYSICS 1 - drwls, Monday, October 20, 2008 at 4:36am
"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
PHYSICS 1 - kelsey, Monday, October 20, 2008 at 4:47am
thank you so much! i figured it out!
- PHYSICS 1 - drwls, Monday, October 20, 2008 at 4:50am
  My pleasure and congratulations! It is great to help students who show their work

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