Momentum Question

Question

A 8.7kg sphere makes a perfectly inelastic collision with a second sphere initially at rest. The composite system moves with a speed equal to the one third the original speed of the 8.7kg sphere. What is the mass of the second sphere ?

Answer 1

m = mass of first sphere = 8.7 kg

M = mass of second sphere = ?

v = initial speed of first sphere

v/3 = speed of composite system

Use conservation of linear momentum.

mv = (m + M)(v/3)

m = (m + M)/3

3m = m + M

M = 2m = 2(8.7 kg) = ? kg