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05/01/2021 6:51 pm
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From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m s-1. Calculate the initial recoil velocity of the rifle.
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05/01/2021 6:57 pm
Initial mass of rifle, m1 = 4 kg Let initial velocity of recoil of rifle = u1
∴ Initial momentum of the rifle = 4 kg × i. Initial mass of bullet, m2 = 50 g = 50/1000 = 0.05 kg
Initial velocity of bullet v2 = 35 m s-1
∴ Initial momentum of bullet = 0.05 kg × 35 m s-1 By the law of conservation of momentum, Momentum of the rifle = Momentum of bullet
m1v1 = -m2v2
4 kg x v1 = -0.05 kg x 35 ms-1
v1 = - \(\frac{0.05 \times 35}{4}\)ms-1
= -0.4375 ms-1
Negative sign indicates that rifle moves in a direction opposite to the direction of bullet.