A ball mass 500g rolls at a velocity of 2m/s and hits another ball of mass 250g

Question

1.What is the velocity of a small ball if the bigger ball immediately stops after collision?
2.What is the velocity of the bigger ball if it rolls in the same direction with the smaller ball at 0.5m/s?

Answer 1

You can answer both questions using conservation of momemtum. You do not have to assume an elastic collision. In fact, neither collision is elastic.

Let the masses of the two balls be M (500 g) and m (250 g). Let Vo be the initial velocity of M.

Let V be the final velocity of the big ball.
Let v be the final velocity of the small ball

1. M*Vo = m*v
v = (M/m)*Vo = 4 m/s

2. M*(2 m/s) = (0.5 m/s)*M + m*v
M*(1.5 m/s) = m*v
v = (M/m)*(1.5 m/s) = 3.0 m/s