A person with a rifle has combined mass 100 kg and stands on a smooth surface. Ten bullets of mass 10 g each are fired horizontally in 5 s with muzzle speed 800 m s⁻¹. Find final recoil speed and average reaction force.
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Question

A person with a rifle has combined mass 100 kg and stands on a smooth surface. Ten bullets of mass 10 g each are fired horizontally in 5 s with muzzle speed 800 m s⁻¹. Find final recoil speed and average reaction force.

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G1 Physics · Accepted Answer

Total fired mass=10×0.010=0.10 kg, carrying forward momentum approximately 0.10×800=80 kg m s⁻¹. Conservation gives recoil speed ≈−80/100=−0.8 m s⁻¹. Mean force magnitude = total bullet momentum/time = 80/5=16 N. Answer: B.