Question

If three trains are moving at the same speed,

then which of the following is correct?

• A. Train $A$ and train $B$ are at rest with respect to each other, but are in motion with respect to train $C$.
• B. Train $A$ and train $C$ are at rest with respect to each other, but are in motion with respect to train $B$.
• C. Train $B$ and train $C$ are at rest with respect to each other, but are in motion with respect to train $A$.
• D. Trains $A$, $B$ and $C$ are at rest with respect to each other.

Answer 1

The correct option is D Trains $A$, $B$ and $C$ are at rest with respect to each other.

Since all the three trains are moving at the same speed, and in the same direction, they are at rest with respect to each other, i.e. one train will appear to be at rest when seen from the other train.
Hence, trains $A$, $B$ and $C$ are at rest with respect to each other.