Question

From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 40 m s–1 . Calculate the initial recoil velocity of the rifle NCERT Class IX Sciences - Main Course Book Chapter 9. Force and Laws of Motion

Answer 1

Given,
Mass of bullet, m1 =50 g=0.05 kg,
The mass of rifle, m2 = 4kg,
Initial velocities of the bullet,u1 = 0,
Initial velocity of rifle, u2= 0,
The final velocity of the bullet, v1= 40 m/sec
Let v2 be the recoil velocity of the rifle.
Then by the law of conservation of momentum
m1u1 + m2u2 = m1v1 + m2v2
or v2= m1v1 / m2= 0.05 × 40/4 = 0.5m/ sec.
Therefore the velocity of rifle is 0.5 m/sec.

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