A ball with a mass of 3 kg is rolling at 15 m/s and elastically collides with a resting ball with a mass of 4 kg. What are the post-collision velocities of the balls?

1 Answer
Feb 15, 2016

v_1=-15/7 m/2
v_2=90/7 m/s

Explanation:

"we must use conservation of momentum to solve this problem."
vec P_1+ vec P_2=vec P_1^'+vec P_2^'
3*15 +0=3*v_1+4*v_2
15+v_1=0+v_2
v_1=v_2-15
3.15=3(v_2-15)+4*v_2
45=3*v_2-45+4*v_2
90=7*v_2
v_2=90/7 m/s
v_1=90/7-15
v_1=-15/7 m/2