Question

A man wearing a bullet-proof vest stands on roller skates. The total mass is 80 kg. A bullet of mass 20 g 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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Answer 1

Answer:

0.1m/s

Explanation:

m - mass of bullet = 0.02 kg

M - mass of man = 80 kg

u - initial velocity of bullet = 400 m/s

U - initial velocity of man =0 m/s

v - final velocity of bullet = 0 m/s

V - final velocity of man

Using conservation of momentum,

initial momentum = final momentum

m⋅u+M⋅U=m⋅v+M⋅V

0.02⋅400+80⋅0=0.02⋅0+80⋅V

8=80⋅V⇒V=0.1 m/s

Therefore, the man moves with a velocity of 0.1 m/s

Answer 2

Answer:

0.1m/s

Explanation: