How many seconds after the departure from the station, the speed of the subway train reaches 72 km / h

How many seconds after the departure from the station, the speed of the subway train reaches 72 km / h, if the acceleration during acceleration is 1 ms.

Problem data: V0 (initial speed of the considered subway train) = 0 m / s; V (required speed) = 72 km / h (in SI V = 20 m / s); a (acceleration of a subway train during acceleration) = 1 m / s2.

The duration of the acceleration of the subway train under consideration is determined by the formula: t = (V – V0) / a.

Let’s perform the calculation: t = (20 – 0) / 1 = 20 s.

Answer: A subway train can accelerate to a speed of 72 km / h in 20 seconds.