Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 9)
9.
Two trains are moving in opposite directions @ 60 km/hr and 90 km/hr. Their lengths are 1.10 km and 0.9 km respectively. The time taken by the slower train to cross the faster train in seconds is:
Answer: Option
Explanation:
Relative speed = (60+ 90) km/hr
| = |  |
150 x | 5 |  m/sec |
| 18 |
| = | |
125 | m/sec. |
| 3 |
Distance covered = (1.10 + 0.9) km = 2 km = 2000 m.
| Required time = | |
2000 x | 3 | sec = 48 sec. |
| 125 |
Discussion:
111 comments Page 12 of 12.
Mosepher said:
3 weeks ago
@RAVI.
The time taken is still 48 seconds.
When two moving objects completely cross each other, the physics of relative motion dictates that the event is symmetrical.
Therefore, whether looking at the slower train crossing the faster one or the faster train crossing the slower one, the elapsed time is identical.
The time taken is still 48 seconds.
When two moving objects completely cross each other, the physics of relative motion dictates that the event is symmetrical.
Therefore, whether looking at the slower train crossing the faster one or the faster train crossing the slower one, the elapsed time is identical.
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