A ball with a mass of 5 kg is rolling at 8 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
May 23, 2016

v_1^'=8/9 " "m/s

v_2^'=80/9" "m/s

Explanation:

m_1=5" "kg
v_1=8" "m/s
P_1=m_1*v_1=5*8=40" " kg*m/s

m_2=4" "kg
v_2=0
P_2=m_2*v_2=4*0=0

Sigma P_b=P_1+P_2" total momentum"
Sigma P_b=40+0=40" "kg*m/s

"post collision velocities :"

v_1^'=(2*Sigma P_b)/(m_1+m_2)-v_1

v_1^'=(2*40)/(5+4)-8

v_1^'=80/9-8

v_1^'=(80-72)/9

v_1^'=8/9 " "m/s

v_2^'=(2*Sigma P_b)/(m_1+m_2)-v_2

v_2^'=(2*40)/(5+4)-0

v_2^'=80/9" "m/s