Speed of train will help us to calculate different types of problems on motion.

1. When a train passes a stationary object:

Let x be the length of the train which includes the engine also. When the end of the train passes the object, then the engine of the train has to move a distance equal to the train.

Then the time taken by the train to pass the stationary object = length of the train/speed of the train

2. When a train passes a stationary object having some length:

When the end of the train passes the stationary object having some length, then the engine of the train has to move a distance equal to the sum of the length of the train and stationary object.

Then the time taken by the train to pass the stationary object = (length of the train + length of the stationary object)/speed of the train

Problems to calculate the motion or speed of train:

**1.** Find the time
taken by a train 150 m long, running at a speed of 90 km/hr in crossing the
pole.

**Solution: **

Length of the train = 150m

Speed of the train = 90 km/hr

= 90 × 5/18 m/sec

= 25m/sec

Therefore, time taken by the train to cross the pole = 150 m/25m/sec = 6 seconds.

**2.** A train 340 m
long is running at a speed of 45 km/hr. what time will it take to cross a 160 m
long tunnel?

**Solution: **

Length of the train = 340 m

Length of the tunnel = 160m

Therefore, length of the train + length of the tunnel = (340 + 160) m = 500m

Speed of the train = 45 km/hr

Speed of the train = 45 × 5/18 m/sec

= 25/2 m/sec

= 12.5 m/sec

Therefore, time taken by the train to cross the tunnel = 500 m/12.5 m/sec.

= 40 seconds.

**3.** A train is
running at a speed of 90 km/hr. if it crosses a pole in just 10 second, what is
the length of the train?

**Solution: **

Speed of the train = 90 km/hr

Speed of the train = 90 × 5/18 m/sec = 25 m/sec

Time taken by the train to cross the pole = 10 seconds

Therefore, length of the train = 25 m/sec × 10 sec = 250 m

**4.** A train 280 m
long crosses the bridge 170 m in 22.5 seconds. Find the speed of the train in
km/hr

**Solution: **

Length of the train = 280 m

Length of the bridge = 170 m

Therefore, length of the train + length of the bridge = 280 m + 170 m = 450 m

Time taken by the train to cross the bridge = 22.5 sec = 45/2 sec.

Therefore, speed of train = 450 m/22.5 m/sec = 450/45/2 m/sec = 20 m/sec

To convert the speed from m/sec to km/hr, multiply by 18/5

Therefore, speed of the train = 20 × 18/5 km/hr = 72 km/hr

**Relationship between Speed, Distance and Time**

**Problems on Calculating Distance**

**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**

**Two Trains Passes in the Same Direction**

**Two Trains Passes in the Opposite Direction**

**8th Grade Math Practice**

**From Speed of Train to HOME PAGE**

**Didn't find what you were looking for? Or want to know more information
about Math Only Math.
Use this Google Search to find what you need.**

## New! Comments

Have your say about what you just read! Leave me a comment in the box below. Ask a Question or Answer a Question.