What Is the Final Speed After Two Hockey Players Collide?

[Precursor]

Homework Statement

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?

Homework Equations

p = mv

p_{i} = p_{f}

The Attempt at a Solution

Here's my interpretation of the image;

http://img696.imageshack.us/img696/1493/momentum.png

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?

 

[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.

 

[Precursor]

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.

Oh, so I need to use sin instead?

 

[rl.bhat]

Oh, so I need to use sin instead?

For your mentioned angle, yes.

 

[Precursor]

Ok, so the new answer is 2.93 m/s.

Thanks for the help