A 100 m long train is running at a speed of 30 km/h. Find the time taken by it to pass a man standing near the railway line.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 12 seconds
To pass a man standing by the line, the train has passed him when its last coach reaches him, so it must cover its own length (the man’s width is taken as nil). The speed is first changed into metres per second, since the length is in metres and the answer in seconds.
Speed in m/s (1 km/h = 5/18 m/s): \(30\times\displaystyle\frac{5}{18}=\frac{25}{3}\,\mathrm{m/s}\)
Time = length \(\div\) speed \(=\displaystyle\frac{100}{25/3}=12\,\mathrm{s}\)