A ball with a mass of 5 kg moving at 2 m/s hits a still ball with a mass of 3 kg. If the first ball stops moving, how fast is the second ball moving?

2 Answers

3.333\ \text{m/sec}

Explanation:

One ball of mass m_1=5kg moving at u_1=2\ m/s hits another ball of mass m_2=3 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)+3(0)=5(0)+3v_2

3v_2=10

v_2=10/3

=3.333\ \text{m/sec}

Jul 5, 2018

~~3.33 meters per second

Explanation:

We use the law of conservation of momentum, which states that:

m_1u_1+m_2u_2=m_1v_1+m_2v_2

where:

  • m_1,m_2 are the masses of the two balls

  • u_1,u_2 are the initial velocities of the two balls

  • v_1,v_2 are the final velocities of the two balls

So, we get:

5 \ "kg"*2 \ "m/s"+3 \ "kg"*0 \ "m/s"=5 \ "kg"*0 \ "m/s"+3 \ "kg"*v_2

v_2=(10color(red)cancelcolor(black)"kg""m/s")/(3color(red)cancelcolor(black)"kg")

~~3.33 \ "m/s"