# Antother Collision

1. Nov 23, 2005

### suspenc3

Antother Collision!!!!!!!!!

A billiard ball moving with a speed of $$v = 2.2m/s$$ strikes an identical stationary ball a glancing blow. After the collision, one ball is found to be moving at a speed of $$v_2 = 1.1m/s$$ in a direction making a $$\theta = 60^o$$ angle with the original line of motion. Find the velocity of the other ball?

I dont really know where to start...Maybe conserving momentum?

2. Nov 23, 2005

### suspenc3

Would I just do this:

$$1/2m_1v_1_i^2 +1/2m_2v_2_i^2 = 2(1/2m_1v_1_f^2) + 1/2m_2v_2_f^2$$

since all of the masses are the same they cancel out and since the second ball is stationary..it is 0

$$v_1_i^2 = 2v_1_f^2 + 2v_2_f^2$$
$$1/2(2.2)^2 = 2sin \theta(1.1)^2 + 2v_2_f^2$$
$$v_2_f = 1.53m/s$$

3. Nov 23, 2005

### Astronuc

Staff Emeritus
Why is the kinetic energy term of m1 doubled on the right hand side?

In an elastic collision, kinetic energy and momentum are conserved. Momentum is conserved in the x and y directions.