What work should be done to stop a train weighing 1000 tons, moving at a speed of 108 km / h.

Initial data: m (train weight) = 1000 t; V1 (the speed at which the train was moving) = 108 km / h; V2 (final speed of the train) = 0 m / s.

SI system: m = 1000 t = 10 ^ 6 kg; V1 = 108 km / h = 30 m / s.

The work that must be done to stop the train will be equal to the change in its kinetic energy: A = Ek1 – Ek2 = Ek1 – 0 = 0.5 * m * V1 ^ 2.

Let’s perform the calculation: A = 0.5 * 10 ^ 6 * 302 = 450 * 10 ^ 6 J = 450 MJ.

Answer: To stop the train, you need to do 450 MJ work.