Question

2. A3 kg ball rolls forward toward a 6 kg ball moving in the opposite direction at 4.6 m/s to

the left. After their collision, the 3 kg ball bounces backward at 4.2 m/s to the left and the 6 kg
ball continues to the left at 1.5 m/s in the same direction. What was the initial velocity of the
3 kg ball?

Answer 1

m1 v1 + m2 v2 = m1 V1 + m2 V2 conservation of momentum

m1 = 3 m2 = 6

v2 = -4.6

V1 = -4.2

V2 = -1.5

v1 = (m1 V1 + m2 V2 - m2 v2) / m1

v1 = (3 * -4.2 + 6 * -1.5 - 6 * -4.6) / 3

v1 = (-12.6 - 9 + 27.6) / 3 = 2 initial velocity of 3 kg ball

Check:

3 * 2 + 6 * -4.6 = -21.6

3 * -4.2 + 6 -1.5 = -21.6