From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m st. Calculate the initial recoil velocity of the rifle.

Explanation

Mass of the rifle, M = 4 k
Mass of the bullet, m = 50 g
`=(50)/(1000)`kg
= 0.05 kg
Initial velocity of the bullet,
`v=35ms^(-1)`
Let initial recoil velocity of the rifle = V = ?
According to the law conservation of momentum,
Total momentum after firing = total momentum before firing
i.e. MV+mv=0
or `V=(mv)/M`
`=(-0.05xx35)/4ms^(-1)`
`=-7/(16)ms^(-1)=-0.44ms^(-1)`
Negative sign shows that the direction of motion of the rifle is opposite to that of the bullet.