Train Passes through a Bridge

When the train passes through a bridge or platform or tunnel or a stationary object having some length

If length of train = x meters and length of the stationery object = y meters.

Also, speed of the train is z km/hr, then time taken by the train to pass the stationary object having length y meters.

= (length of the train + length of stationary object)/speed of the train

= (x meters + y meters)/z km/hr

Note: Change km/hr to m/sec.

Solved examples to calculate when the train passes through a bridge or a stationary object having some length.

1. A train 175 m long crosses a bridge which is 125 m long in 80 seconds. What is the speed of the train?

Solution:            

Length of the train = 175 m.       

Length of the bridge = 225 m

Distance covered by the train to cross the bridge = (175 + 225) m

                                                                   = 400 m

Time taken by the train to cross the bridge = 80 seconds

Speed = distance/time

         = 400/80 m/sec

         = 5 m/sec.


2. A train 220 m long is running at a speed of 36 km/hr. What time will it take to cross a 110 m long tunnel?

Solution:            

Length of the train = 220 m

Length of the tunnel = 110 m

Therefore, length of the train + length of the tunnel = (220 + 110) m = 330m

Speed of the train = 36 km/hr   

Speed of the train = 36 × 5/18 m/sec = 10 m/sec

Therefore, time taken by the train to cross the tunnel = 330 m/10 m/sec.

                                                                         = 33 seconds.


3. Find the time taken by 150 m long train passes through a bridge which is 100 m long, running at a speed of 72 km/hr.

Solution:            

Speed of train = 72 km/hr = 72 × 5/18 m/sec = 20 m/sec

In order to cross a bridge of length 100 m, the train will have to cover a distance = (150 + 100) m = 250 m

Thus, speed = 20 m/sec and distance = 250 m

Time = distance/speed

       = 250m/20 m/sec

       = 25/2 sec

       = 12.5 sec.                                                                    


4. A 90 m long train is running at a speed of 54 km/hr. If it takes 30 seconds to cross a platform, find the length of the platform.

Solution:            

Speed of the train = 54 km/hr = 54 × 5/18 m/sec = 15 m/sec

Time taken to cross the bridge = 30 sec

Distance covered by train to cross the platform = speed × time

                                                                = (15 × 30) m

                                                                = 450 m

To cross the platform, train covers a distance = length of train + length of platform

                                                     450 m = 90 m + length of platform

Therefore, length of platform = (450 – 90) m = 360 m

Speed of Train

Relationship between Speed, Distance and Time

Conversion of Units of Speed

Problems on Calculating Speed

Problems on Calculating Distance

Problems on Calculating Time

Two Objects Move in Same Direction

Two Objects Move in Opposite Direction

Train Passes a Moving Object in the Same Direction

Train Passes a Moving Object in the Opposite Direction

Train Passes through a Pole

Train Passes through a Bridge

Two Trains Passes in the Same Direction

Two Trains Passes in the Opposite Direction






8th Grade Math Practice

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