Question

Our textbook describes a common model for friction (both static and kinetic) in which the area of contact between interacting surfaces is irrelevant to the size of the frictional force. However, we can't help noticing how wide the tires are on drag racing cars! One explanation for the large size of the tires would be to give a larger contact patch between the tire and the track in search of more traction. But our model says contact area doesn't matter. Clarify this situation in a mini essay of 2 or 3 sentences. Sort out whether contact area matters or not. Can you think of other advantages of really wide tires?

Answer 1

Frictional force is given by F=mg.

Where is the coefficient of friction. m is mass of the body and g is the acceleration due to gravity.

So, its evident that frictional force does depend on the area of contact between two interacting bodies. But its true that wider tyres have better traction. The main reason is the composition of the tyre. Soft materail tyres need to be wider so they can withstand the weight of the vehicle and they have large coefficient of friction and hence better grip. Whereas, thin tyres cannot support the weight of the vehicle, have low coeffient of friction between road and tyre and hence less grip. Moreover, thin tyres wear out much quicker and has to be replaced.