At a speed of u1 = 15 km / h, the braking distance of the car is s1 = 1.5m.

At a speed of u1 = 15 km / h, the braking distance of the car is s1 = 1.5m. What will be the braking distance s2 at a speed of u2 = 90 km / h? Acceleration is the same in both cases.

Data: V1 (initial speed) = 15 km / h (in SI V1 = 4.17 m / s); S1 (initial braking distance) = 1.5 m; V2 (considered speed) = 90 km / h (in SI V2 = 25 m / s); a (acceleration) = a1 = a2.

1) Let us express the acceleration of the car: Sx = Vx ^ 2 / 2a, whence a = Vx ^ 2 / 2Sx.

2) Determine the second braking distance: V1 ^ 2 / 2S1 = V2 ^ 2 / 2S ^ 2, whence S2 = V2 ^ 2 * 2S1 / 2V1 ^ 2 = V2 ^ 2 * S1 / V1 ^ 2 = 25 ^ 2 * 1, 5 / 4.17 ^ 2 = 54 m.

Answer: At a speed of 90 km / h, the braking distance will be 54 m.