The plane, flying at a speed of 720 km / h, is landing. The time until the plane stops completely is 25 s.

The plane, flying at a speed of 720 km / h, is landing. The time until the plane stops completely is 25 s. Calculate the length of the runway.

Initial data: Vн (the speed with which the aircraft began to land) = 720 km / h; V (the plane will stop) = 0 m / s; t (travel time to complete stop) = 25 s.

SI system: Vн = 720 km / h = 720 * 1000/3600 m / s = 200 m / s.

1) Let’s calculate the acceleration of the aircraft: V = Vн + a * t.

a = (V – Vн) / t = (0 – 200) / 25 = -8 m / s ^ 2 (slow motion).

2) Determine the length of the runway:
S = Vn * t + a * t ^ 2/2 = 200 * 25 – 8 * 25 ^ 2/2 = 2500 m.

S = (V ^ 2 – Vn ^ 2) / 2a = (-200 ^ 2) / (2 * (-8)) = 2500 m.