A ball with a mass of 5 kg is rolling at 3 m/s and elastically collides with a resting ball with a mass of 2 kg. What are the post-collision velocities of the balls?

1 Answer
Feb 20, 2016

v_1=9/7 m/s
v_2=30/7 m/s

Explanation:

5*3+0=5*v_1+2*v_2
15=5*v_1+2*v_2" (1)"
3+v_1=0+v_2" (2)"
color(red)"'the sum of the velocities of objects before and after collision must be equal'"
"write " v_2=3+v_1" at (1)"
15=5*v_1+2*(3+v_1)
15=5.v_1+6+2*v_1
15-6=7*v_1
9=7*v_1
v_1=9/7 m/s
use :" (2)"
3+9/7=v_2
v_2=30/7 m/s