A 70-kg man is standing in a 20-kg boat.Thinking he is stepping out onto the dock,the man steps to the right.However,the following will actually happen (ignore the friction of the water or air on the boat or the man):
A) The man only moves a short distance to the right while the boat moves a larger distance to the left.
B) The man actually stays still while the boat moves toward the left.
C) The boat doesn't move and the man moves to the right.
D) None of the above.

Question

Quizplus · Accepted Answer

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. When the man steps to the right, he exerts a force on the boat toward the left. To maintain their center of mass, the boat also moves to the left, but since it has less mass, it moves a larger distance than the man. Therefore, the man only moves a short distance to the right while the boat moves a larger distance to the left.

A 70-Kg Man Is Standing in a 20-Kg Boat