A ball with a mass of $5 kg$ is rolling at $5 m/s$ 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 · 2016-05-28T09:21:46

$v_1^'=5/9" "m/s$

$v_2^'=50/9" "m/s$

$m_1=5" " kg$
$vec v_1=5 " "m/s$

$vec P_1=m_1*vec v_1$
$vec P_1=5*5=25 " "kg*m/s" momentum before collision for object " m_1$

$m_2=4" "kg$
$vec v_2=0$

$vec P_2=m_2*vec v_2=4*0=0" the object with " m_2= 4 kg" has no momentum"$

$Sigma vec P_b=25+0=25 " "kg*m/s" total momentum before collision"$

$"post collision velocity of object with "m_1="5 kg"$

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

$v_1^'=(2*25)/(5+4)-5$

$v_1^'=50/9-5$

$v_1^'=50-45/9$

$v_1^'=5/9" "m/s$

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

$v_2^'=(2*25)/(5+4)-0$

$v_2^'=50/9" "m/s$

A ball with a mass of 5 kg 5 kg is rolling at 5 m/s5 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?