A truck weighing 6 tons, moving at a speed of 36 km / h, braked to a stop for 30 seconds. Find the braking force.

1. From the condition of the problem, it is assumed that the movement of the truck is uniformly accelerated:

m = 6 t = 6000 kg;

v0 = 36 km / h = 36 * 1000 m / 3600 s = 10 m / s;

v = 0;

t = 30 s;

v = v0 + at. (1)

2. From equation (1) we determine the acceleration of the truck:

at = v – v0;
a = (v – v0) / t;
a = (0 – 10) / 30 = -1/3 (s).
3. Let’s calculate the braking force:

F = ma = 6000 * (-1/3) = -2000 (N).

A minus sign means that the braking force is directed against the movement of the truck.

Answer: 2000 N.