Banking Roads

When vehicle go through turnings, they travel along a nearly circular arc. There must be some force to produce the required centripetal acceleration. Centripetal force is provided to the vehicle by following three ways.

• By friction only
• By banking of roads only
• By friction and banking of roads both

Definition

The phenomenon of raising outer edge of the curved road above the inner edge is to provide necessary centripetal force to the vehicles to take a safer turn and the curved road is called Banking of Roads.In order to avoid skidding, while going round a curved path the outer edge of the road is raised above the level of the inner edge. This is known as banking of curved roads or tracks.

Introduction

When a vehicle goes round a curved road, it requires some centripetal force. While rounding the curve, the wheels of the vehicle have a tendency to leave the curved path and regain the straight line path. Force of friction between wheels and the roads opposes this tendency of the wheels. This force of friction therefore, acts towards the centre of circular track and provides the necessary centripetal force. Imagine vehicle of weight mg'(acts vertically downwards) is moving on a level curved road. R1 and R2 are the forces of normal reaction of the road on the wheels. These are vertically upward since road is leveled. Hence,

R1 + R2 = mg

Let F1 & F2 are forces of frictions between tyre and road directed towards centre of curved road.

F1 = μ R1

F2 = μ R2

where μ is coefficient of friction between tyres and road. If 'v'is the velocity of the vehicle while rounding the curve, the centripetal force required is mv²/r. As this force is provided by the force of friction therefore

Hence the maximum velocity with which a vehicle can go round a level curve; without skidding is