# Homework Help: 2D momentum of two objects next to a wall

1. Nov 24, 2009

### Jeriho

1. The problem statement, all variables and given/known data
We have two pucks next to a wall. Puck 1 has velocity v0=15 m/s in the direction y (as seen on the picture). Puck 2 is stationary. After the collision puck 1 moves in the opposite direction with velocity v1=10 m/s and puck 2 moves with unknown velocity in the direction x. The radius of puck 1 is r1=3cm and of puck 2 r2=6cm. The mass of puck 1 is m1=0.1kg and of puck 2 m2=0.5kg. The collision is not elastic.

What is the velocity of puck 2 after the collision?

http://img134.imageshack.us/img134/8082/breznaslova.jpg [Broken]

2. Relevant equations
Equation of momentum P=mv
Pythagorean theorem c2=a2+b2

3. The attempt at a solution
First I calculated the angle using the radiuses of the pucks and I got Cos($$\alpha$$)=$$\frac{r2-r1}{r2+r1}$$
I got that $$\alpha$$ = 70.5 degrees.

Then I went on to figure out momentums. I figured out this:
http://img256.imageshack.us/img256/8120/breznaslova2.jpg [Broken]
The angle between P0 and P2 is $$\alpha$$.
Then I went on to make the P1 the hypotenus and the opposite is P1y which is the same as P=m1v1. From that I calculated the angle and then the adjacent P1x. Am I right to think that the velocity I am looking for is vx=$$\frac{P1x}{m2}$$.

Thanks for any assistance.

Last edited by a moderator: May 4, 2017
2. Nov 24, 2009

### Jeriho

Does noone have an idea how to do this?

3. Feb 5, 2010

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