# Homework Help: Hockey Stick Momentum problem

1. Feb 28, 2010

### Precursor

1. The problem statement, all variables and given/known data
Two 72.0 kg hockey players skating at 5.45 m/s collide and stick together. If the angle between their initial directions was 115$$^{o}$$, what is their speed after the collision?

2. Relevant equations
p = mv

$$p_{i} = p_{f}$$

3. The attempt at a solution

Here's my interpretation of the image;

http://img696.imageshack.us/img696/1493/momentum.png [Broken]

$$p_{ix} = p_{fx} = 0$$

$$p_{iy} = p_{fy}$$

$$m_{A}v_{A} + m_{B}v_{B} = (m_{AB})(v_{AB})$$

$$(72)(5.45cos(32.5)) + (72)(5.45cos(32.5)) = 144v_{AB}$$

$$v_{AB} = 4.60 m/s$$

Am I correct?

Last edited by a moderator: May 4, 2017
2. Feb 28, 2010

### rl.bhat

P*cosθ components of the two players get canceled according to the diagram given by you . Check the other components. Your calculation will be correct if you use θ = 57.5 degrees.

3. Feb 28, 2010

### Precursor

Oh, so I need to use sin instead?

4. Feb 28, 2010