Two fat astronauts each of mass 120 kg are travelling in a closed spaceship moving at a speed of 15 km/s in the outer space far removed from all other material objects. The total mass of the spaceship and its contents including the astronauts is 660 kg. If the astronauts do slimming exercise and thereby reduce their masses to 90 kg each, with what velocity will the spaceship move?


The spaceship is moving in vacuum and there is absolutely no external force acting on it. Change in masses won’t affect the speed of the ship as there is no gravitational force affecting the motion of the spaceship.

Velocity of the spaceship = same as before = 15 km/s


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