An object of mass 1 kg travelling in straight line with a velocity of `10 ms^(-1)` collides with it and sticks to a stationary wooden block of mass 5 kg. Then both move off together in the same straight line. Calculate the total momentum before the impact and just after the impact. Also calculate the velocity of combined object.

Explanation

Mass of the object, `m_(1) = 1 kg`
Initial velocity, `u = 10 ms^(-1)`
Mass of stationary wooden block, `m_(2) = 5kg`
Let velocity of the combined object = v
Total momentum just before impact
`= m_(1) xx u`
`= 1kg xx 10ms^(-1)`
`= 10 kg ms^(-1)`
By law of conservation of momentum
Total momentum just before impact = Total momentum just after impact
`therefore` Total momentum just after impact `= 10 kg ms^(-1)`
Total momentum of the combined object
`= (m_(1) + m_(2)) xx v`
`= (1 kg + 5 kg) xx v`
`therefore 10 = 6v`
or `v = (10)/(6) = (5)/(3) ms^(-1)`