Question

A 0.30 kg metal ball at a velocity of 3.0 m/s hits another metal ball with a mass of 0.20 kg which is at rest. What is the velocity of the 0.20-kg metal ball if the velocity of the 0.30-kg metal ball became 2.0 m/s after the collision? Use: p before the collision (m₁v₁ + m₂v₂) = p after the collision (m₁’v₁’ + m₂’v₂’)

Answer 1

The law of conservation of momentum says

$$m_1v_1+m_2v_2=m_1v_1'+m_2v_2'$$ $$v_2=0$$

Hence

$$v_2'=\frac{m_1}{m_2}(v_1-v_1')$$

$$v_2'=\frac{0.30}{0.20}(3.0-2.0)=1.5\:\rm m/s$$