# Rotational Kinematics (Ball hits stick)

1. Jan 10, 2010

### amnestic

1. The problem statement, all variables and given/known data
A 1 kg ball is traveling horizontally at 10 m/s. It hits a stick of mass 1kg and length 1.2m (rotational inertia 1/12 M L^2) at the bottom of the stick, which rotates upward 90 degrees from its previous location. The ball's direction changes by an angle theta. Find theta and the new velocity.

2. Relevant equations
U potential=mgh
K=(1/2)mv^2
L=Iw
K=(1/2)Iw^2

3. The attempt at a solution
U of stick=(1)(9.8)(.6)=5.88
This equals Kinetic Energy lost
5.88=(1/2)(1)(v^2)
v=3.43
10-3.43=6.57m/s

I have no idea how to find the theta though. I don't understand why the ball would even change direction. Wouldn't it just go the same direction at a slower pace?

Last edited: Jan 10, 2010
2. Jan 10, 2010

### Matterwave

I'm not sure this problem is possible, without at least knowing where on the stick the ball hit and how fast the stick was moving...

3. Jan 10, 2010