Two hockey players collide and stick, what is V final?

Question

Two 78.0 kg hockey players skating at 6.25 m/s collide and stick together.

If the angle between their initial directions was 130 degrees, what is their speed after the collision?

I'm using momentum=mass times velocity.
also,
How does the 130 degrees come into play?

Answer 1

Momentum is conserved in each dimension.

Let the motion of the first skater define the x axis. Then the second skater is moving at an angle of 130 degrees relative to the +x axis, or 50 degrees above the -x axis.

Initial x momentum:

( 78 kg ) ( 6.25 m / s ) + ( 78 kg ) ( 6.25 m / s ) cos 50 degrees

Final x momentum:

( 2 ) ( 78 kg ) Vx

Set initial momentum = final momentum and solve for Vx

Initial y momentum:

0 + ( 78 kg ) ( 6.25 m / s ) ( sin 50 )

Final y momentum:

( 2 ) ( 78 kg ) Vy

Set the initial and final momenta equal and solve for Vy.

You now have the components of their motion and can easily find the magnitude and direction.