Question

Two boys A and B with masses 30 kg and 20 kg respectively are at the two extremes of a boat of mass 50 kg and length 5 m resting still on water. Boys A and B move towards each other and meet at the midpoint of the boat. During the process, the distance moved by the boat and boys is (Neglect friction between water and boat)

• A. 50 cm
• B. 2 m
• C. 2.5 m
• D. 25 cm

Hint:

In problems involving the motion of objects on a boat, always apply the principle of conservation of momentum to find distances moved by different objects.

Answer 1

The Correct Option is A

Since no external horizontal forces act on the system, the center of mass of the system remains stationary. Initially, the center of mass is at rest, and as the boys move towards each other, the boat moves in the opposite direction to conserve momentum. The mass of the boat and the boys results in the boat moving a small distance compared to the boys. The total distance moved by the boat and boys is 50 cm.