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Problem 11 - Entrance Test

A bullet of mass 10 g is fired from a gun with a velocity of 400 m/s. If the gun recoils with a velocity of 1 m/s, what is the mass of the gun?

Correct: B

Using the principle of conservation of momentum, m₁v₁ + m₂v₂ = 0. Here, m₁ = 0.01 kg, v₁ = 400 m/s, and v₂ = -1 m/s. So, 0.01 * 400 + m₂ * (-1) = 0. Thus, m₂ = 4 kg.