A man weighing `60kg` runs along the rails with a velocity of `8km//h` and jumps into a car of mass 1 quintal standing on the rails. Calculaate the velocity with which car will start travelling along the rails.

Explanation

Here, mass of man, `m_(1)=60kg` ,
initial velocity of a man, `u_(1)= (18km)/h= (18 xx 1000 m)/(60 xx 60s)= 5m//s`
mass of car, `m^(2)` = 1 quintal =100 kg , initial velocity of car, `u_(2)=0`
After the man jump into the car, let their common velocity be v
Applying the principle of conservation of momentum, total momentum after jump = total momentum before jump.
`(m_(1)+m_(2)) v= m_(1)u_(1)+m_(2)u_(2)` or `(60+100) v = 60xx5+100xx0` or `v= (300)/(160)= 1.88m//s`.