Looks like man doesn't like speed

Classical Mechanics Level 1

Two trains are running at 40 km/hr and 20 km/hr respectively in same direction.Fast train completely passes a man sitting in the slower train in 5 seconds. what is the length of the fast train?

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Manish Mayank by Manish Mayank , 20, India

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1 solution

Let's start by getting the difference in the speeds. 40 k m h r − 20 k m h r = 20 k m h r 40 \frac{km}{hr} - 20 \frac{km}{hr} = 20 \frac{km}{hr} Now, convert that to m s \frac{m}{s} 20 k m h r ∗ 1 h r 60 m i n ∗ 1 m i n 60 s e c ∗ 1000 m 1 k m = 50 9 m s 20 \frac{km}{hr} * \frac{1 hr}{60 min} * \frac{1 min}{60 sec} * \frac{1000 m}{1 km} = \frac{50}{9} \frac{m}{s} So, the fast train's length is the difference of speed times the time it took to pass a man from the slow train. 50 9 m s ∗ 5 s e c = 250 9 m \frac{50}{9} \frac{m}{s} * 5 sec = \frac{250}{9} m

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