A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system ?

Question

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Answer 1

The child is running arbitrarily on a trolley moving with velocity V. However, the running of the child will produce no effect on the velocity of the centre of mass of the trolley. This is because the force due to the boy’s motion is purely internal. Since no external force is involved in the boy–trolley system, the boy’s motion will produce no change in the velocity of the centre of mass of the trolley.

Answer 2

The child is running arbitrarily on a trolley moving with velocity V. However, the running of the child will produce no effect on the velocity of the centre of mass of the trolley. This is because the force due to the boy’s motion is purely internal. Since no external force is involved in the boy–trolley system, the boy’s motion will produce no change in the velocity of the centre of mass of the trolley.

A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system ?

A man weighing 80 kg is standing on a trolley weighing 320 kg. The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley along the rails at a speed 1 ms $^{- 1}$ then after 4 second his displacement relative to the ground will be :

A man of mass $M$ stands at one end of a stationary plank of length $L$ , lying on a smooth surface. The man walks to the other end of the plank. If the mass of the plank is $\frac{M}{3}$ , the distance that the man moves relative to the ground is :

the velocity of the CM of the rod.

Two particles $A$ and $B$ , initially at rest, moves towards each other under a mutual force of attraction. At the instant when the speed of $A$ is $v$ and the speed $B$ is $2 v$ , the speed of centre of mass is :

Revise with Concepts

Block Pulled by Rope of Some Mass

Solving Problems in Mechanics

A child sits stationary at one end of a long trolley moving uniformly with a speed V on a smooth horizontal floor. If the child gets up and runs about on the trolley in any manner, what is the speed of the CM of the (trolley + child) system ?

A man weighing 80 kg is standing on a trolley weighing 320 kg. The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley along the rails at a speed 1 ms−1 then after 4 second his displacement relative to the ground will be :

A man of mass M stands at one end of a stationary plank of length L, lying on a smooth surface. The man walks to the other end of the plank. If the mass of the plank is 3M​, the distance that the man moves relative to the ground is :

the velocity of the CM of the rod.

Two particles A and B, initially at rest, moves towards each other under a mutual force of attraction. At the instant when the speed of A is v and the speed B is 2v, the speed of centre of mass is :

Revise with Concepts

Block Pulled by Rope of Some Mass

Solving Problems in Mechanics

A man weighing 80 kg is standing on a trolley weighing 320 kg. The trolley is resting on frictionless horizontal rails. If the man starts walking on the trolley along the rails at a speed 1 ms $^{- 1}$ then after 4 second his displacement relative to the ground will be :

A man of mass $M$ stands at one end of a stationary plank of length $L$ , lying on a smooth surface. The man walks to the other end of the plank. If the mass of the plank is $\frac{M}{3}$ , the distance that the man moves relative to the ground is :

Two particles $A$ and $B$ , initially at rest, moves towards each other under a mutual force of attraction. At the instant when the speed of $A$ is $v$ and the speed $B$ is $2 v$ , the speed of centre of mass is :