The aircraft reduced its speed from 720 to 180 km / h within 20 seconds.

The aircraft reduced its speed from 720 to 180 km / h within 20 seconds. With what acceleration did the plane fly and what distance did it fly during this time?

Task data: V0 (initial speed) = 720 km / h (in SI V0 = 200 m / s); V (final speed) = 180 km / h (in SI V = 50 m / s); t (deceleration duration) = 20 s.

1) Aircraft acceleration: a = (V – V0) / t = (50 – 200) / 20 = -7.5 m / s2.

2) The distance that the given plane flew in 20 s: S = (V + V0) * t / 2 = (50 + 200) * 20/2 = 2500 m (2.5 km).

Check: S = V0 * t + 0.5 * a * t ^ 2 = 200 * 20 + 0.5 * (-7.5) * 20 ^ 2 = 2500 m (correct).

Answer: The plane flew 2.5 km with an acceleration of -7.5 m / s2.