A train with a mass of 4000 tons, moving at a speed of 36 km / h, began to brake. In 1 minute

A train with a mass of 4000 tons, moving at a speed of 36 km / h, began to brake. In 1 minute the train traveled 510 m. What is the friction force acting on the train?

Problem data: m (mass of a given train) = 4000 t (in SI m = 4 * 10 ^ 6 kg); V0 (speed before braking) = 36 km / h (in SI system V0 = 10 m / s); t (braking duration) = 1 min (in SI t = 60 s); S (distance traveled) = 510 m.

The friction force acting on a given train is determined by the formula: Ftr. = m * a = m * (V0 * t – S) * 2 / t2 (acceleration is expressed from the formula: S = V0 * t – a * t ^ 2/2).

Let’s make a calculation: Ftr. = 4 * 10 ^ 6 * (10 * 60 – 510) * 2/60 ^ 2 = 200 * 10 ^ 3 N (200 kN).