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Force and Laws of Motion
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02/11/2021 4:42 pm
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A man wearing a bullet-proof vest stands still on roller skates. The total mass is 80 kg. A bullet of mass 20 grams is fired at 400 m/s. It is stopped by the vest and falls to the ground. What is then the velocity of the man?
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02/11/2021 4:45 pm
Mass of the man, m1 = 80 kg
Speed of man, v1
Mass of bullet m2 = 20 g = 0.02 kg
Speed of bullet v2 = 400 m/s
Acc. to law of conservation of momentum
m1v1 = m2v2
80 x v1 = 0.02 x 400
v1 = \(\frac{400 \times 0.02}{80}\) = 0.1 m/s