Question

A 2.69 kg sphere makes a perfectly inelastic collision with a second sphere that is initially at rest. The composite system moves with a speed equal to one fifth the original speed of the 2.69 kg sphere. What is the mass of the second sphere?   

Plese help!!

Answer 1

$m_{1}V_{o1}+m_{2}V_{o2}=(m_{1}+m_{2})V$

$m_{1}V_{o1}=(m_{1}+m_{2})V$

Isolating the mass $m_{2}$,

$m_{2}=m_{1}\left ( \frac{V_{o1}}{V}-1 \right )=m_{1}\left ( \frac{5V}{V}-1 \right )=4m_{1}=4(2.69Kg)$

or

${\color{Blue} m_{2}=10.8\, Kg}$