Exams › NEET › Physics

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 it 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:

1. 3.0 m
2. 2.3 m
3. zero
4. 0.75 m

Correct answer: zero

Solution

The boat-man system is isolated horizontally because the water is still and no external horizontal force acts on it. Therefore, the centre of mass of the system remains unchanged.

Related NEET Physics questions

• Two point masses $m$ and $M$ with $M>m$ are placed at two different positions. Where does the centre of mass of this two-body system lie?
• Two uniform solid spheres A and B have masses $m$ and $2m$ and radii $2a$ and $a$, respectively. They are placed just touching each other. How far is the centre of mass of the system from the centre of sphere A?
• The centre of mass of a system is best described as the point:
• A ball is thrown vertically upward from the surface of the Earth. Considering the Earth-ball as an isolated system (ignoring air), which statement best describes the motion of both during the ball's upward journey?
• Object P has mass $200\,\text{g}$ and velocity $10\,\text{m s}^{-1}$ along the $+x$-direction. Object Q has mass $500\,\text{g}$ and velocity $(3\hat{i}+5\hat{j})\,\text{m s}^{-1}$. What is the speed of their centre of mass?
• Two masses in the ratio $n:1$ are connected by a light inextensible string over a frictionless pulley (Atwood machine). After the system is released from rest, what is the acceleration of the centre of mass of the two-mass system?

⚔️ Practice NEET Physics free + battle 1v1 →