Vehicle Performance (2)

Vehicle Performance (2)

 

Gradient Resistance

This resistance force is originated from the gravity. If the road is up-hilled shape then we need stronger traction than plane road. If we can describe this resistance as an simple equation, it will be like below.

 

G-Resistance » Weight x sine (Road Gradient)

 

 

 

Rolling Resistance

This resistance comes from the contacting surface between tire and road. When the tire is rolling and propelling the vehicle forward, the tire and road deforms itself and this deformation acts as a resistance force. Somebody can ask that pressurized tire will not give any resistance, but the rolling resistance is not negligible at all specially when the vehicle runs at high speed.

 

 

 

Imagine that we are running at a sand beach, we feel that it is much harder to run than that of paved road, this “hard” running comes from the deformation of sand. Just same situation happens when the vehicle runs on the road. If we describe this resistance force in a simple equation, it will be like below.

 

R-Resistance » Weight x ( Coefficient of R-Resistance + Speed )

  

Acceleration Drag

To give a movement to a stand-still thing, or to accelerate a thing which moves with a constant speed, we need to apply force. The amount of force can be calculated by the 2^nd Law of movement (The Law of acceleration) from sir Newton, the product of mass and acceleration.

 

F = m x a  ( Force = Mass x Acceleration )

 

When a vehicle moves, the traction force and these four kinds of resistance force always apply to the vehicle. If the traction force is bigger than the sum of resistance forces, the car has still the margin of power to accelerate itself. This means if we push the acceleration pedal more, we can still accelerate the vehicle. But as soon as the resistance force is same or bigger than traction force, we cannot accelerate the vehicle any more.

 

 

 

We call the speed of this point (traction force is same as resistance force) as maximum speed of the vehicle. Now you can understand the relationship between traction and resistance of a moving vehicle. Any kind of super car has a maximum speed because the resistance force always exists as far as the vehicle runs on the earth. ...henry kim

 

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