A train of length 800 metres is running at a speed of 60 km/hr.How much time will it take pass a tunnelvof length 200 meters ?

Question

Try to solve it.

Answer 1

60 km     1000 meters         1 hour            1 min

-------- * --------------  * -------------- * ------------- = 16 and 2/3  meters per second

1 hour        1 km                60 min            60 sec

 

 

Now, we must determine how far the train actually travels

in order to clear the tunnel, with respect to and from the perspective

of the front of the train. Drawing a picture will help!

 

Consider the following time frames in increments of 200 meters.

 

1) the front of the train is entering the tunnel..... 0 meters traveled thus far.

 

The train travels 200 meters......

 

2) The front of the train is at the exit of the tunnel. The first 200 meters of

     the train is inside the tunnel, and 600 meters of it are sticking outside

     the back of the tunnel..... 200 meters in total traveled thus far.

 

The train travels another 200 meters.....

 

3)  The front of the train is 200 meters past the exit of the tunnel.

      200 meters of the train are inside the tunnel. 400 meters of the train

      are sticking out the back end of the tunnel.... 400 meters in total

      traveled so far.

 

The train travels another 200 meters.....

 

4) The front of the train is 400 meters past the exit of the tunnel.

     200 meters of the train are inside the tunnel. 200 meters of the

     train are sticking out of the back end of the tunnel. 600 meters in total.

 

The train travels another 200 meters....

 

5) The front of the train is 600 meters past the exit of the tunnel.

    200 meters of the train are inside the tunnel. 800 meters traveled

    this far in total.

 

The train travels another 200 meters....

 

6) The front of the train is 800 meters past the exit of the tunnel.

     THe train has cleared the tunnel. 

 

The train must travel 1000 km to clear the tunnel.

 

You may think 800/200 = 4. But at that point the last

200 meters of the train are still inside the tunnel.

Again, drawing a picture helps a lot!

 

distance = rate x time

 

1000 meters = 16 and 2/3 meters per second x time

 

t = 1000 meters / 16 and 2/3 meters per second

 

  = 1000 / 16 and 2/3

 

  = 1000 / 50/3

 

 = 3000/50

 

 = 60

 

The train will clear the tunnel in exactly 60 seconds or 1 minute