Question

A ball with a mass of `5` `kg` moving at `2` `ms^-1` hits a still ball with a mass of `6` `kg`. If the first ball stops moving, how fast is the second ball moving?

Answer 1

`v_2=5/3 m/s`

Explanation:

`"Total momentum before collision:"`
`....................................................`
`P_1=m_1*v_1" "P_1=5*2=10`
`P_2=m_2*v_2" "P_2=6*0=0`
`Sigma P_b=P_1+P_2`
`Sigma P_b=10+0`
`Sigma P_b=10 kg*m/s`

`"Total momentum after collision:"`
`..................................................`
`P_1=5*0" "P_1=0`
`P_2=6*v_2`
`Sigma P_a=P_1+P_2`
`Sigma P_a=0+6*v_2`
`Sigma P_a=6*v_2`

`"Conservation of momentum"`
`............................................`
`Sigma P_b=Sigma P_a`
`10=6*v_2`

`v_2=10/6`

`v_2=5/3 m/s`