# Puck Collision

1. Nov 5, 2007

### Jtappan

1. The problem statement, all variables and given/known data

Two identical pucks are on an air table. Puck A has an initial velocity of 2.6 m/s in the positive x-direction. Puck B is at rest. Puck A collides elastically with puck B and A moves off at 2.50 m/s at an angle of +16.3° above the x-axis. What is the speed and direction of puck B after the collision? (Take angles above the x axis to be positive and below to be negative.)
_____ m/s at -73.7 °

2. Relevant equations

??????????

3. The attempt at a solution

I got the angle but I have no idea what the speed would be. Does anybody have like a ball park figure of what it would be? because the answers i get dont even make sense.

2. Nov 5, 2007

### Midy1420

velocity is a vector so you find it by finding the resultant vector if you have the angle then you must have Vx and Vy, therefore you can find V

3. Nov 5, 2007

### Jtappan

no i dont have Vx and Vy, i just applied the physics of pool where hitting a ball on another ball will result in a total angle of 90 degrees. So i do not know where or how to find the V.

4. Nov 5, 2007

### catkin

In an elastic collision you will have conservation of momentum and energy. That gives you 3 equations to work with because you have momentum in both the x direction and perpendicular to it -- the y direction?

5. Nov 6, 2007

### learningphysics

you've got the direction. just use a mass m for the puck. what is the total energy before the collision in terms of m. let vb be the velocity of puck B after the collision. what is the total energy after the collision in terms of m and vb...

set the energy before = energy after.

solve for vb.