A man in a spacecraft that is moving with a velocity V₀ in free space runs forward and then stops.The center of mass of the system (that is,the ship and the man) A)slows while the man is running,then speeds up when he stops. B)slows while the man is running,then resumes its original velocity when he stops. C)moves faster while the man is running,then slows when he stops. D)moves faster while the man is running,then resumes its original velocity when he stops. E)continues all the while at its original velocity.

Question

Quizplus · Accepted Answer

The motion of the man inside the spacecraft does not affect the velocity of the center of mass of the system. This is because the man and the spacecraft are both considered as a single system. The net external force acting on this system is zero, hence according to the law of conservation of momentum, the velocity of the center of mass of the system stays constant. Therefore, the center of mass of the spacecraft-man system continues all the while at its original velocity.

A Man in a Spacecraft That Is Moving with a Velocity