### Motion of a car on a circular level road

1. Consider a car of weight mg going around on a circular turn of radius r with constant velocity v on a level road as shown in following figure. While taking the round, the tyres of the car tend to leave the road and move away from the centre of curve. Hence the forces of friction f_{1} and f_{2} will act inward at the inner and the outer tyres respectively. If R_{1} and R_{2} are the normal reactions of ground on the tyres, then

f_{1} =μ_{s}R_{1} and f_{2} = μ_{s}R_{2}

Where μs is the coefficient of static friction between the tyre and the road

Hence, total frictional force

f = μ_{s}R_{1} + μ_{s}R_{2} = μ_{s}(R_{1} +R_{2})= μ_{s}R

Where R is the reaction of the ground on the car.

2. Because the total frictional force f cannot exceed μsR, therefore we may write

f ≤ μ_{s}R

This frictional force will provide the necessary centripetal force f i.e., f = (mv^{2}/r)

Hence, mv^{2}/r ≤ μ_{s}R ……………….(1)

As total normal reaction balances the weight of the car, hence R =mg …………..(2)

From equation (1) and (2), we get

mv^{2}/r ≤ μ_{s}mg or

v^{2} ≤ μ_{s}rg or

v ≤ √μ_{s}rg

Therefore, the maximum velocity (Vmax) with which a car can travel on level curved road is given by

V _{max} = √(μ_{s}rg)

If the car is driven at a speed greater than V_{max}, then the car will skip and go off the road in a circle of radius greater than r. This is because even the maximum available friction will be in adequate to provide the necessary centripetal force.