# Hockey Puck Collision--momentum problem

mtruong1999

## Homework Statement

"Hockey puck A sliding on ice with velocity 10 m/s in the x direction collides at a glancing blow with a second stationary puck B. Puck A scatters at an angle of θA= 40 degrees above the x axis, while B slides away at an angle ofθB= 50 degrees below the x axis. (a) Use momentum conservation to find the final speeds vA and vB of the two pucks, respectively. What is the change in kinetic energy? (b) What are the two scattering angles according to an observer in the center of mass frame of reference?"

## Homework Equations

mAv1A + mBv1B = mAv2A + mBv2B

## The Attempt at a Solution

Ok, so far I divided the problem into x and y components, where the final velocities in the x direction would be v2Acos40 and v2Bcos50 and the final velocities in the y direction would be v2Asin40 and -v2Bsin50. I feel like there are too many unknowns, we aren't given the masses of the two pucks, and I have absolutely no clue how to do this problem without the masses of the pucks. I have 4 unknowns (final velocities and the masses) and only two equations. Am I missing something??? How do I approach this problem??

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TSny
Homework Helper
Gold Member
Assume the pucks have equal mass.

• mtruong1999
mtruong1999
Assume the pucks have equal mass.
Then the masses will cancel out?? BRILLIANT, that makes a lot of sense, thank you!