Question

Ball B, with a mass of 30kg, is moving to the left at 10 m/s. With what velocity should ball A, with a mass of 10kg, move to the right and collide with 2, so that Ball A rebounds with a velocity of 30 m/s, and Ball B with velocity of 10 m/s? Assume the collison to be perfectly elastic.

Answer 1

using the conservation of momentumwhere momentum = mass x velocity
so the let x be the initial velocity of the ball B

(30 kg) (-10 m/s) + (10 kg) (x) = (30 kg) (30 m/s) + ( 10 kg) (-10 m/s)
-300 + 10 x = 900 - 10010x = 900 - 100 + 30010x = 1100x = 1100 / 10x = 110 m/s