Question

A train 150 m long completely passes a boy walking in the opposite direction at 6km/hr in 9 second. and a car travelling in the opposite direction in 6 second. Find the speed of the car.
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Answer 1

Answer:

The length of the train = L = 150 meters

The train cross the boy walking in opposite direction

The speed of boy = s = 6 km/h

Or, The speed of boy = 1.67 m/s

The time taken by train to cross the boy = t = 9 seconds

Let The speed of the train = S m/s

According to question

∵ Distance =  Speed × time

i.e Length = (S + s) × t

Or, L  =  (S + s) × t

Or,  150 m = (S + 1.67) m/s × 9 s

Or, 16.67 = S + 1.67

∴ S = 16.67 - 1.67

i.e S = 15 m/s

So, The speed of the train = 15 m/s = 54 km/h

Again

A car travelling in opposite direction to train

The train cross the car in time = T = 6 seconds

Let The speed of the car = x m/s

And The speed of train = S = 15 m/s

∵ Distance =  Speed × time

Length = (S + x) m/s × T

Or, 150 = (15 + x) × 6

Or, 150 = 90 + 6 x

Or, 6 x = 150 - 90

Or, 6 x = 60

x = 10 m/s

So, The speed of the car = x = 10 m/s = 36 km/h

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