A man is standing at an edge of a boat. He starts moving towards the centre of the boat. As no external force is acting on the system of boat and man, (neglect friction due to water) the boat will move in opposite direction.
Initially, the total momentum was zero and after the man starts moving, the total momentum would still be zero as no external force is acting on the system of the man and the boat (law of conservation of momentum). So, the boat will move in the direction opposite to the direction of motion of the man. |