# Inelastic Collisions

1. Feb 21, 2006

### Huskies213

Can anyone tell me what i am doing wrong for this problem?
Two 75 kg hockey players skating at 5.75 m.s collide and stick together. If the angle btween their initial directions was 125 degrees, what is their velocity after the collision?

I used the formula Vf = m1v1/(m1+m2) cos 125 for the x value which is supposed to come out to be 1.23 m/s

and the same formula Vf = m1v1/(m1+m2) sin 125 for the y value which is supposed to come out to be 2.36 m/s.

Thanks !

2. Feb 21, 2006

### Staff: Mentor

Go back to basics with conservation of momentum:
$$m_1\vec{v_1} + m_2\vec{v_2} = (m_1 + m_2)\vec{v_f}$$

Establish x and y axes, and write expressions for momentum conservation for each direction separately.

Hint: If you define your x-axis to be along the line bisecting that 125 degree angle, your momentum calculations will be greatly simplified.