Acar goes forward along a level road at constant velocity. the additional force needed to bring the car into equilibrium is

Frictional force

Explanation:

Since the body is moving at constant velocity, this means that the acceleration of the body is zero. Frictional force is a force of opposition which tends to oppose the moving force of an object on a flat surface.

Mathematically, summation of force on the car along the road will be

Fm - Ff = ma

Fm = moving force

Ff = frictional force

m = mass of the body

a = acceleration of the body

Since a = 0, we have;

Fm -Ff = 0

Fm = Ff (which shows that the two forces acting on the body are equal and opposite)

This frictional force will tend to keep the body at equilibrium.

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .