Question

There are some passengers inside a stationary railway compartment. The centre of masses of the compartment itself(without the passengers) is C1, while the centre of mass of the compartment plus passengers' system is C2. if the passengers moves about inside the compartment

• A. both C1 and C2 will move with respect to the ground
• B. neither C1 nor C2 will move with respect to the ground
• C. C1 will move but C2 will be stationary with respect to the ground.
• D. C2 will move but C1 will be stationary with respect to the ground.

Answer 1

The correct option is C

C1 will move but C2 will be stationary with respect to the ground.

Since the compartment (including passenger) is stationary the combined centre of mass of the compartment and passengers is fixed, i.e C ₂ is fixed.When the passengers move here and there in the compartment then in an attempt to keep C ₂ fixed C ₁ has to move.