Question

The following three trains are moving at the same speed.
Choose the correct option.

• 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.

It is given that all the three trains are moving at the same speed.
Also, looking at the engines, we can infer that all the three trains are moving in the left direction, i.e. the same direction.

When such a condition happens, the objects are at rest with respect to each other. Hence, each 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.