Question

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

Answer 1

by conservation law of momentum
m1v1=m2v2
4 × v1 = 0.05 × 35
v1=0.4375

Answer 2

Mass of rifle = M = 4×10³g

mass of bullet = m = 50 g

velocity of bullet = v = 35m/s

velocity of rifle = V = ?
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Momentum of rifle = momentum of bullet

MV = mv

V= mv/M

V = 50×35/4×10³

V = 0.4375 m/s