Question

A young hockey player stands at rest on the ice holding a 1.3-kg helmet. The player tosses the helmet with a speed of 4.6 m/s in a direction 13° above the horizontal, and recoils with a speed of 0.27 m/s. Find the mass of the hockey player.

Answer 1

Its another momentum problem similar to your other post. Since there is only two 'fragments' from the 'explosion' :P you can disregard the angle for the velocity and act like they are horizantal to each other. If you don't want to disregard the angle, then you may use component method and find the two component momentums then use pythagorean theorom.
Easier way is to just impose they're horizantal, therefore:
m1v1=-m2v2 (since they are going in different directions, the momentums will be the negative of each other).
You have two velocities and a amss, sub for the final mass.