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JEE MainPhysicsCenter of Mass, Momentum and Collision

A soldier holds a machine gun and can exert a maximum average force of 140 N to keep it stationary. The gun fires bullets of mass 50 g at a speed of 400 m/s. The maximum number of bullets that the soldier can fire per minute is :

Options

  1. A420
  2. B7
  3. C42
  4. D70

Correct answer

A. 420

Step-by-step solution

The average force exerted by the gun is equal to the rate of change of momentum of the bullets. Let n be the number of bullets fired per second. F = n m v Given F = 140 N, m = 50 g = 0.05 kg, and v = 400 m/s. 140 = n 0.05 400 140 = n 20 n = 7 bullets per second. The number of bullets fired per minute is 7 60 = 420 . Answer: 420

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