2. 350 m.
Problems on Trains:
1. A train moves past a telegraph post and a bridge 300 m long in 10 seconds and 25 seconds respectively. What’s the speed of the train?
Solution:
Let the distance and speed be x and y respectively.
Time = x/y = 10.
y = x/10
Speed = Length / time
x/10 = (x+300)/ 25
x = 200 m.
The speed of the train = 200/10
= 20 m/s
= 20*18/5
= 72 km/hr.
2. How many seconds will a 200 m long train take to cross a man walking with a speed of 2 km/hr in the direction of the moving train if the speed of the train is 42 km/hr?
Solution:
Relative speed = 42-2 = 40 km/hr
= 40*5/18
= 100/9 m/s.
Time = 200*9/100
= 18 seconds.
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