# Approaching the station, the train decelerates for 20 seconds. Determine the braking distance of the train

July 27, 2021 | education

| **Approaching the station, the train decelerates for 20 seconds. Determine the braking distance of the train if its initial speed is 72 km / h.**

V0 = 72 km / h = 20 m / s – the initial speed of the train;

t = 20 s – the time during which the train decelerates.

It is required to find the braking distance S.

Since the speed of the train after stopping is 0, then the acceleration of the train is a = V0 / t.

S = V0 * t – a * t ^ 2/2 = V0 * t – V0 * t ^ 2 / t * 2 = V0 * t – V0 * t / 2 = V0 * t / 2 = 20 * 20/2 = 200 meters.

Answer: the braking distance is 200 meters.

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