A man standing on very slick ice fires a rifle horizontally. The mass of the man together with the rifle is 70 kg, and the mass of the bullet is 10 g. If the bullet leaves the muzzle at a speed of 500 m/s, what is the final speed of the man?

Final speed of the man is 0.071 m/s

Explanation:

Here momentum is conserved.

Momentum of bullet = Moment of man plus rifle after firing

Mass of bullet = 10 g = 0.01 kg

Speed of bullet = 500 m/s

Momentum of bullet = Mass of bullet x Speed of bullet = 0.01 x 500 = 5 kg m/s

Mass of man plus rifle = 70 kg

We need to find speed of man

Moment of man plus rifle after firing = Momentum of bullet = 5 kg m/s

Mass of man plus rifle x Speed of man = 5

70 x Speed of man = 5

Speed of man = 0.071 m/s

Final speed of the man = 0.071 m/s