Question

A ball with a mass of `12 kg` moving at `6 m/s` hits a still ball with a mass of `16 kg`. If the first ball stops moving, how fast is the second ball moving?

Answer 1

`u_1=-6/7 " m/s"`

`u_2=36/7" m/s"`

Explanation:

`m_1=12" "kg`
`v_1=6" "m/s`
`P_1=12*6=72" " kg*m/s`

`P_2=0`

`P_b=P_1+P_2=72+0=72 " "kg*m/s`

`"post collision velocities..."`

`u_1=(2*P_b)/(m_1+m_2-v_1`

`u_1=(2*72)/(12+16)-6`

`u_1=144/28-6`

`u_1=(144-168)/28" "u_1=-24/28=-6/7 m/s`

`u_2=(2*P_b)/(m_1+m_2-v_2`

`u_2=(2*72)/(12+16)-v_2`

`u_2=(2*72)/(12+16)-0`

`u_2=144/28=36/7 " "m/s`