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QPages 456-457: Q2: HC Verma: Concepts of Physics - Volume 2 The Special Theory of Relativity Pages 456-457: Q2 Solution: A uniformly moving train passes by a long platform. Consider…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often confuse the proper frame with the frame where the time interval is shortest or the frame of the 'stationary' object. Remember that the proper frame is strictly defined as the inertial frame where the two events occur at the same spatial coordinate ($\Delta x = 0$), which here is the train frame because the engine is at a fixed position relative to the train.

A uniformly moving train passes by a long platform. Consider the events 'engine crossing the beginning of the platform' and 'engine crossing the end of the platform'. Which frame train frame or the platform frame) is the proper frame for the pair of events?

Step-by-Step Verified Solution

**Answer:** The train frame is the proper frame for the pair of events. **Step-by-Step Explanation:** The two events are: 1. Engine crossing the beginning of the platform. 2. Engine crossing the end of the platform. In the train frame, both events occur at the same spatial location (the engine). A frame in which two events occur at the same place is the **proper frame** for those events. Hence, the train frame is the proper frame .

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