A 10 kg object collides with stationary 5 kg object and after collision they stick together and move forward with velocity `4 ms^(-1).` What is the velocity with which the 10 kg object hit the second one ?

Options

A. `4 ms ^(-1)`
B. `6 ms^(-1)`
C. `10 ms ^(-1)`
D. `12 ms ^(-1)`

Answer

B

Explanation

`m _(1) u _(1) + m _(2)u _(2) = ( m _(1) + m _(2))v `
`implies 10 xx u _(1) + 5 xx 0 = ( 10 + 5) xx 4`
`implies u _(1) = ( 15 xx 4)/(10 ) = 6 ms ^(-1)`