Question

Find the speed of the train if a train crosses a bridge of 800 m in 160 seconds and a man who is standing on the platform in 1 minutes.
1. 5 m/s
2. 6 m/s
3. 7 m/s
4. 8 m/s
5.

Answer 1

Correct Answer - Option 4 : 8 m/s

Given: 

Length of a bridge = 800 m

Train crosses a bridge in 160 seconds

Train crosses a man standing on the platform in 1 minutes

Formula used:

Time = (L_Train + L_Platform)/S_Train 

where, L_Train is Length of the train, L_Platform is Length of the platform

S_Train is Speed of the train

Calculations:

Let the speed of the train be y

According to the question, we have

When a train crosses a man standing on the platform

⇒ Time = L_Train/y

⇒ 60 = L_Train/y   

⇒ LTrain = 60 × y      ----(1)

When a train crosses a bridge

Time = (LTrain + LPlatform)/y

⇒ 160 = (LTrain + 800)/y       ----(2)

Put the value of equation (1) in (2), we get

⇒ 160y = (60y + 800)

⇒ 160y - 60y = 800

⇒ 160y - 60y = 800

⇒  100y = 800

⇒ y = 800/100

⇒ y = 8 m/s

∴ The speed of the train is 8 m/s.