Question

A train 150 m long is running with a speed of 68 km/h. In what time will it pass a man who is running at 8 km/ h in the same direction in which the train is going?

Answer 1

Given :-

▪ A train 150 m long is running with a speed of 68 km/h .

▪ At the same time, A man is running at 8 km/h in the same direction.

To Find :-

▪ Time at what the train will pass the man.

Solution :-

Since the man is also running in the same direction as that of train. So, Let us find the relative velocity of the train with respect to train.

⇒ Rel. Velocity = Velocity of train - velocity of man

⇒ Rel. Velocity = 68 - 8

⇒ Rel. Velocity = 60 km

Now, The size of man as compared to the train can be assumed as a point object which the train have to pass. In other words, The train will have to travel its own length.

So, We have

• Distance = 150 m or 0.15 km
• Speed = 60 km/hr

⇒ Distance = Speed × Time

⇒ 0.15 = 60 × Time

⇒ Time = 0.15 / 60

Since the time would be in hour if calculated this way, but we should find it in seconds, because that will be more simpler. But, 1 hour = 3600 seconds

So, we have

⇒ Time = 0.15 / 60 × 3600

⇒ Time = 0.15 × 60

⇒ Time = 9 seconds

Hence, The train will pass the man in 9 seconds.

Answer 2

Given : A train 150 m long is running with a speed of 68 km/h. In what time will it pass a man who is running at 8 km/hr in the same direction.

　

To find : Speed of train.

　

Calculations :

→ 68 - 8

→ 60

　

→ 150 × 60 × 60/60 × 1000

→ 540000/60000

→ 9 seconds

　

Therefore, 9 seconds is the speed of the train.