Question

A boat floats in a lake. When the boat moves the force of resistance is proportional to the velocity of the boat. Initially the boat is at rest. A person walks from the stern to the bow of the boat. What will be the position of the boat long time after the person stopped moving?

Answer 1

Answer: Contant.

Explanation:

You are given that When the boat moves the force of resistance is proportional to the velocity of the boat. This means that the total momentum on the boat is equal to zero. Then the boat remains at a certain position.

When a person walks from the stern to the bow of the boat, the boat will tend to move in the opposite direction with equal magnitude of momentum. The magnitude of forces will thereby cancel out.

The person will be seen moving while the boat moves in the opposite direction.

If no external force is acting on the boat, the sum of the momentum of the person and the boat will be equal to zero. And the boat will remain at rest.

The position of the boat long time after the person stopped moving will therefore remain the same.