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?

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Answer 1 · 2016-05-23T07:44:48

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

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

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

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

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

$"post collision velocities :"$

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

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

$v_1^'=80/9-8$

$v_1^'=(80-72)/9$

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

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

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

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

A ball with a mass of 5 kg 5 kg is rolling at 8 m/s8 m/s and elastically collides with a resting ball with a mass of 4 kg4 kg. What are the post-collision velocities of the balls?