Banking of roads
The banking angle of the curved road provides required centripetal force for the vehicle to make a safe turn.
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.
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 center of circular track and provides the necessary centripetal force.
The force of friction is not a reliable source for providing the required centripetal force to the vehicle. Especially in hilly areas where the vehicle has to move constantly along the curved track, the maximum speed at which it can run will be very low. If any attempt is made to run it at a greater speed, the vehicle is likely to skid and go out of track. In order that the vehicle can go round the curved track at a reasonable speed without skidding, the sufficient centripetal force is managed for it by raising the outer edge of the track a little above the inner edge. It is called banking of the circular track or Banking of Roads.
More Banking angle implies a safe speedy turn:
A bus driving around a sharp corner at a speed of 100 kmph on a heavily banked road.
Following forces are involved :
- The weight ‘Mg’ acting vertically downwards
- The reaction ‘R’ of the ground to the vehicle acting along normal to the banked road in upward direction.
- The vertical component R.Cos θ of R will balance the weight of the vehicle.
- The horizontal component R.Sin θ of R will provide necessary centripetal force to the vehicle.
Roads are generally banked for the average speed of vehicles passing over them. However, if the speed of a vehicle is somewhat less or more than this, the self adjusting state friction will operate between tire and road and vehicle will not skid.