When approaching the stations, the train reduced its speed by 10m / s for 20s. With what acceleration did the train move?

Acceleration is the ratio of the speed difference to the time interval during which this speed change occurred:
a = (V-Vо) / t
V-Vо = -10m / s – the speed difference is negative, because train slows down
t = 10c
a = (V-Vо) / t = -10 / 20 = -0.5 m / s2

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