A ball with a mass of 6 kg is rolling at 7 m/s and elastically collides with a resting ball with a mass of 3 kg. What are the post-collision velocities of the balls?

1 Answer
May 11, 2016

v_1^'=7/3 m/s
v_2^'=28/3 m/s

Explanation:

6*7+3*0=6*v_1^'+3*v_2^'" conservation of momentum"

42=6*v_1^'+3*v_2^'" "(1)

v_1+v_1^'=v_2+v_2^'" conservation of the kinetic energy"

7+v_1^'=0+v_2^'" (2)"

42=6*v_1^'+3(7+v_1^')

42=6v_1^'+21+3v_1^'

42-21=9v_1^'

21=9v_1^'

v_1^'=21/9

v_1^'=7/3 m/s

"use (2)"

7+7/3=v_2^'

v_2^'=28/3 m/s