A ball with a mass of 5kg moving at 2 m/s hits a still ball with a mass of 9 kg. If the first ball stops moving, how fast is the second ball moving?

1 Answer

1.111 \ \text{m/s}

Explanation:

One ball of mass m_1=5kg moving at u_1=2\ m/s hits another ball of mass m_2=9 kg at rest u_2=0. After collision, the first ball stops i.e. v_1=0 & second ball moves with a velocity of v_2 in the initial direction of first ball then

By the conservation of momentum in moving direction of first ball

\text{momentum before collision}=\text{momentum after collision}

m_1u_1+m_2u_2=m_1v_1+m_2v_2

5(2)+9(0)=5(0)+9v_2

9v_2=10

v_2=10/9

v_2=1.111 \ \text{m/s}