# How Cars are avoiding Resistance of air, tyre rolling, gradient – What is tractive effort – Important of a card design

## What is air resistance

Air resistance On the road the blowing wind against the direction of the vehicle and the opposing force due to the vehicle speed oppose the vehicle to move front. This opposing force is called as the air resistance. To find the air resistance of a vehicle, the following formula can be used.

Air resistance (Ra ) = Ka A.V^2

where,

A = frontal area of the vehicle, in m2 V = Velocity of the vehicle in km/hr
Ka = Co-efficient of air resistance,=0.0032 (car) = 0.0046 (truck and lorry) ## Rolling resistance

When the vehicles wheel is rolling  on the road, due to the mud, sand, pits, ups and down conditions of the road causes a resistance on the vehicle from its movement. This opposing force is called as the rolling resistance. The Rolling resistance of a vehicle can be calculated by using the formula
Rolling resistance (Rr ) = K.W

Where,

W = Weight of the vehicle, Kg
K = Rolling Constant = 0.005 for good road. = 0.18 for mud road.

When a vehicle claims on the mountains or high bridges, the complete weight of the vehicle is dragged backwards because of the gravitational force which causes opposing force acting on the vehicle. This opposing force is called as gradient resistance. The gradient Resistance can be calculated by using the following formula
Gradient Resistance (RG) = W sin θ

Where,

W = Weight of vehicle, Kg
θ = Angle between straight and inclined Road

## Tractive effort

When the vehicle is rolling on the road the frictional force between the top of the road and the tyre surface which is in contact on the road is called as the tractive effort. ### Traction

Traction is defined as the action which maintains or transfers the tractive effort as same.