Question

Why do the heavy vehicles have large number of wheels?

Answer 1

The pressure produced by a given force depends on the area of the surface on which it acts. The greater the surface area, the lesser pressure is produced. Load carrying heavy vehicles are provided with large number of wheels so that the load (weight, force) is distributed over larger surface area of the wheels in contact with the road. Hence, the pressure decreases and the tyres dont get stuck in the ground.