Answer:
We know the momentum after the collision MUST be equal to the momentum BEFORE the collision. Â
Momentum is a VECTOR quantity having both magnitude and direction. Â The first ball has momentum P =m*v = 2*4 = 8 at 90degrees. Â The second ball has momentum P = 1*8 = 8 at -90 or 270 degrees. Â They sum to zero when you perform vector addition.
Explanation: