How can I calculate the speed of two hockey players after a collision?

[BraedenP]

Homework Statement

Two 72.0kg hockey players skating at 5.75 m/s collide and stick together. If the angle between their initial directions was 125^o, what is their speed after the collision?

Homework Equations

P=mv

The Attempt at a Solution

I set up a vector diagram with their initial directions 125^o apart. I set one vector to straight forward to make calculations easier.

I worked out that one momentum vector would be 414 $$kg\cdot m/s$$ forward, and the other vector would have magnitudes of roughly 339

and 651 [forward].

Adding the components, I arrived at a new combined momentum of 734$$kg\cdot m/s$$. Since this equals the momentum of BOTH players, I divided that by $$(72\cdot 2)$$ to get the final speed. This was wrong.

I also tried using kinetic energy, but that answer was wrong as well.

How would I go about solving such a question?

Thanks!​

 

[Delphi51]

That 651 can't be right. Has to be less than 414. And it has to be negative.

 

[BraedenP]

I can't believe it.. I used numbers from the wrong part of the question in my solution. Those aren't the right numbers at all.

Believe it or not, using the right numbers solved the question! Thanks. :P