# Conservation of Angular Momentum Help

1. Dec 13, 2014

### Speedking96

1. The problem statement, all variables and given/known data
Below is the question:

I only have an issue with the last step of the problem. Why wouldn't you factor in the translational AND rotational energy of the ball and then solve for maximum height?

2. Dec 13, 2014

### jbriggs444

The translational kinetic energy of the ball is the rotational kinetic energy of a system consisting of the ball alone when using a reference axis such that the ball's radial velocity is zero.

3. Dec 13, 2014

### Stephen Tashi

In a real life problem you'd have to do that. In this problem, you have no information that would allow you to calculate a specific number for the rotation rate for the 5 kg ball. You don't know the diameters of the balls. The book expects you to treat them as "point masses".

Without considering friction or the deformation of the objects,, how could the bar impart any rotation to the 5 kg ball?

4. Dec 13, 2014

### Speedking96

Alright, I understand. Thank you.