At what speed did a train weighing 1.500 tons move if, under the action of a resistance force of 150kn

At what speed did a train weighing 1.500 tons move if, under the action of a resistance force of 150kn, it traveled 500m before braking.

Problem data: m (train mass) = 1500 t (in SI m = 1.5 * 10 ^ 6 kg); Fcopr (force of resistance to movement, braking force) = 150 kN (in SI Fcopr = 150 * 10 ^ 3 N); S (train path to stop) = 500 m.

We express the speed with which the train was supposed to move from the formula: Fcopr = m * a = m * V02 / 2S, whence V0 = √ (Fcopr * 2S / m).

Let’s perform the calculation: V0 = √ (150 * 10 ^ 3 * 2 * 500 / (1.5 * 10 ^ 6)) = 10 m / s.

Answer: Before the start of braking, the speed of the train was 10 m / s.