A train with a mass of m = 500 T, after stopping the traction of the locomotive under the action of a friction force equal

A train with a mass of m = 500 T, after stopping the traction of the locomotive under the action of a friction force equal to Ftr. = 98 kN, stopped after t = 1 minute. How fast was the train going?

Given:

m = 500 tons = 500 * 10 ^ 3 kilograms – train weight;

F = 98 kN = 98 * 10 ^ 3 Newton – the friction force acting on the train;

t = 1 minute = 60 seconds – the time interval from the start of braking to the complete stop of the train.

It is required to determine v (m / s) – the speed of the train before braking.

Let’s find the acceleration with which the train braked:

a = F / m = 98 * 10 ^ 3 / (500 * 10 ^ 3) = 98/500 = 0.2 m / s ^ 2.

Since the final speed of the train is zero (the train stopped), then:

v = a * t = 0.2 * 60 = 12 m / s.

Answer: before braking, the train was traveling at a speed of 12 m / s.