A train with a mass of 1,000 tons stops when braking in 20 s, having covered a distance of 150 m

A train with a mass of 1,000 tons stops when braking in 20 s, having covered a distance of 150 m. Find the initial speed of the train and the braking force if it was moving equally slowly.

Given:
m = 1000 t = 10 ^ 6 kg – train mass
S = 150 m – braking distance of the train
t = 20 s – train time
V = 0 – final speed of the train
V0 -?
F -?
S = V0 * t – a * t ^ 2/2, where a is the acceleration of the train
a = (V – V0) / t
a = V0 / t
S = V0 * t – V0 * t ^ 2/2 * t = V0 * t – V0 * t / 2 = V0 * t / 2
V0 = 2 * S / t
V0 = 2 * 150/20 = 15 m / s
In order to find the force, we use Newton’s second law:
F = m * a
a = V0 / t
F = m * V0 / t
F = 10 ^ 6 * 15/20 = 750,000 N = 750 kN