Question

Two object, each of mass `1.5 kg`, are moving in the same straight line but in opposite directions, The velocity of each object is `2.5 ms^(-1)` before the collision during which they stick together. What will be the velocity of the combined object after collision?

Answer 1

Correct Answer - `0 ms^(-1)`
Mass of one of the objects, `m_(1) = 1.5 kg ` Mass of the other object, `m_(2) = 1.5 kg`
Velocity of m1 before collision, `u_(1) = 2.5 m//s`
Velocity of` m_(2)` , moving in opposite direction before collision, `u_(2) = -2.5 m//s`
Let v be the velocity of the combined object after collision. By the law of conservation of momentum:
Total momentum after collision = Total momentum before collision
Or,`= (m_(1) + m_(2)) v=m_(1)u_(1) + m_(2) u_(2) `
Or,` = (1.5 + 1.5) v =1.5xx2.5 + 1.5 xx(-2.5)` [negative sign as moving in opposited direction ]
Or, `v=0ms^(-1)`