Q. Two persons of masses 55 kg and 65 kg respectively, are at the opposite ends of a boat. The length of the boat is 3.0 m and weighs 100 kg. The 55 kg man walks up to the 65 kg man and sits with him. If the boat is in still water the centre of mass of the system shifts by
A) 0.75 m
B) 3.0 m
C) 2.3 m
D) zero
Explanation
[Solution from source] The man, the other man and the boat form an isolated system with no external horizontal force (still water, friction-free), so the centre of mass of the system cannot move. The boat moves back as the man walks, but the common centre of mass shifts by zero. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.