a 0.060-kg tennis ball, initially moving at a speed of 12m/s, is struck by a racket causing it to rebound in the opposite direction at a speed of 18m/s. what is the change in momentum of the ball?

Question

alfie · Answer

Well, the momentum is equal to mass * velocity.
Therefore you first find the initial momentum, then the second one and take the difference.

anonymous · Answer

so would i also have to use this formula: ma*va+mb*vb= ma*va'+mb*vb'?

alfie · Answer

Uhm, I am not sure. I would just do it with:
Initial momentum = Mass * velocity-initial.
Final momentum = mass * velocity-final.

Since velocity is a vector, you have to be careful with your coordinate system, then since it asks for the change in momentum, I guess it's asked to know how much the initial momentum differs from the second one, therefore take the difference.

anonymous · Answer

ok thanks