Question

From a rifle of mass 4kg, a bullet of mass 50g is fired with an initial velocity of 35 ms-1. Calculate the initial recoil velocity of the rifle.

Answer 1

from a rifle of mass 4kg, a bullet of mass 50g is fired with an initial velocity of 35m/s. calculate the initial recoil velocity of the rifle. Answer: Since no external force acts on the rifle, the change in momentum is zero.

Answer 2

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Given :-

⇒ Mass of rifle (M) = 4 kg

⇒ Mass of bullet (m) = 50 g = 0.05 kg

⇒ Velocity of rifle (v) = 35 m/s

⇒ Recoil velocity of rifle (V) = V m/s

Concept :-

★ Apply Conservation of momentum ,

It states that initial momentum of the system is equals to final momentum .

Initial momentum = ( M + m ) u

Initially , system is in rest

⇒ Initial momentum = ( M + m ) 0

⇒ Initial momentum = 0 Kg-m/s

This momentum is equals to final momentum , a/c to the conservation of momentum .

Solution :-

➠ 0 = MV + mv

➠ 0 = (4)V + (0.05)(35)

➠ 4V = - 1.75

➠ V = - 0.4375 m/s

Note : - ve sign of recoil velocity of rifle denotes opposite direction to the motion of velocity of bullet