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QPage 458: Q10: HC Verma: Concepts of Physics - Volume 2 The Special Theory of Relativity Page 458: Q10 Solution: Two babies are born in a moving train, one in the compartment…

⚠️ Common Exam Traps & Conceptual Pitfalls

When using Δt' = γ(Δt - vΔx/c^2) for a train moving forward, set Δx as the spatial separation from the back to the front event. Since Δx>0, Δt' is negative, meaning the front event happens earlier in the ground frame. Swapping the sign or the order of events gives the opposite, incorrect answer.

Two babies are born in a moving train, one in the compartment adjacent to the engine and other in the compartment adjacent to the guard. According to the train frame, the babies are born at the same instant of time. Who is elder according to the ground frame?

Step-by-Step Verified Solution

**Answer:** The baby born in the compartment adjacent to the engine is elder. **Step-by-Step Explanation:** In the train frame, both babies are born simultaneously. In the ground frame, the train is moving. The compartment adjacent to the engine is **ahead** in the direction of motion. Events simultaneous in the moving frame are not simultaneous in the ground frame; the event ahead occurs **earlier** in the ground frame. Hence, the baby near the engine is elder .

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