Air Resistance, Tyres and Friction
Uploaded by Buttwhisker on May 25, 2000
Dragsters use a combination of large wide tyres or the rear and small narrow tyres on the front this combination is used for the following reasons:rho is the air density, which we cannot change.
The front wheels:
The front wheels are very narrow. This is so a minimum of air resistance or drag affects the dragster with lower drag better acceleration an in turn a better top speed can be achieved all leading to a better pass (race time).
Now lets try to understand the concept of air resistance and drag. A basic example is placing your hand out the window with your palm facing forwards as you are driving your car along at about sixty kilometres per hour. You will feel a strong force of the wind (air resistance) pushing back at your hand. Now turn your hand side or so that your little finger is facing the front and your thumb is facing the rear at the same speed. The force of air resistance exerted on your hand is greatly reduced. This force is similar as to that exerted on the front wheels of the dragster.
Now dragsters reach speeds of up to five hundred kilometres per hour, imagine the force needed to hold your hand against the wind if your palm was facing the front. It would be much easier to hold your hand side on. The same as it would be much easier for the dragsters engine to push the narrow front wheels compared to large ones.
Air resistance is a form of friction (namely fluid friction) a friction from the air, as we know friction is defined as a force that opposes movement.
The formula used to determine aerodynamic drag is as follows:
Drag = 0.5 * rho * Cd * v2 * S
Aerodynamic drag is a function of the following:
v2 is velocity squared which is endeavoured to be maximized for the best time and/or pass.
S is the frontal or cross sectional area which we want to minimize. I.e. less frontal area means that a less significant amount of air resistance impedes the top speed and acceleration.
Cd is the coefficient of drag, which we want to minimize.
So the two things with which can be worked with or changed, the frontal area and coefficient of drag, both of which need to be to minimized for the best results.
Having very narrow front wheels minimizes the...