# Finding angular momentum

1. Dec 1, 2015

### MARK STRETERS

1. The problem statement, all variables and given/known data
A metal bar of length r is attached to a pivot point at (0,0) in the XY plane. A steel ball is projected toward the free end of the rod and strikes it at the tip. Show how to calculate the angular acceleration of the bar after the collision and draw a vector diagram to scale to show your result makes sense. The initial velocity of the ball is 22m/s in magnitude and it is moving at 40 degrees relative to the horizontal. After the collision, which last for .001 sec, the ball is moving at 15 m/s in magnitude with a direction of 22 degrees relative to the horizontal. The mass of the ball and the rod is 43g and the rod is 65 cm long.

2. Relevant equations
The one relevant equation we were given was I = 1/3 MR^2

3. The attempt at a solution
1. Calculated angular momentum of ball = r*m*v_y before and after collision. Subtracted the two to get total L(angular momentum)
2. w = 3*L/(mr^2)
3. Divided angular velocity by duration of collision.

But I got something in the 30 thousands and I believe the answer should be in the 20 thousands so something is wrong with the way that I am solving this.

2. Dec 1, 2015

### insightful

More details are needed. Could you post a diagram?