Question

A train $150m$ long passes a tree in $12seconds$. How long will it take to pass a tunnel $250m$ long?

Answer 1

Step 1: Calculate speed

Distance covered by the train is same as the length of the train = $150m$

Time taken = $12seconds$

We can find the speed of the train and we know that speed is given in terms of distance covered and time taken as :

$speed=\frac{dis\tan cecovered}{timetaken}$

$speed=\frac{150}{12}m/s=12.5m/s$

Step 2: Find time taken

Length of the tunnel = $250m$

To cross a tunnel the distance covered by the train = length of tunnel + length of train

Distance covered = $250+150m=400m$

We know that to calculate time taken when speed and distance covered is given we use the formula:

$$\begin{gathered} timetaken=\frac{dis\tan cecovered}{speed} \\ timetaken=\frac{400}{12.5}s=32s \end{gathered}$$

Hence, the time taken by the train to pass a tunnel $250m$ long is $32seconds$.