Question

A high pressure tire rolls more easily than a low pressure tire because:
(A) Rolling friction is less in high inflated tire
(B) Rolling resistance is more in high inflated tire
(C) Rolling resistance is zero in high pressure tire
(D) Friction is zero in high pressure tire

Answer 1

Hint: When a tyre revolves then it has only a part of its surface which is in contact with the ground. In a low pressure tire, the area of contact of tyre with road is more because of the shape of the tyre. In a low pressure tire, the contact area is more so there is high rolling resistance as compared to the high pressure tire.

Complete solution:
Tyres of any vehicle are made up of synthetic rubber polymers. During each revolution of tyres, the tyre is in direct contact with the road. During the contact of that particular surface of the tyre, it is compressed and then it expands as soon as it leaves the surface. However, for each revolution, the compression and expansion are not perfectly elastic. Due to this non elastic behaviour there is some heat loss in the form of friction.
For a high pressure tire, the tyre (or the rubber surface) that is in contact with the road is less as compared to a low pressure tire. The reason for this statement is that the lower the tire pressure, the more rubber that is in contact with the road for each revolution the greater is the heat loss in form of friction.
The increased heat losses adds up to lower fuel economy.
Therefore, a highly pressure tire rolls more easily than a low pressure tire because rolling resistance is more in a high inflated tire.

Thus, option (B) is the correct choice.

Note: Rolling friction is the resistive force offered by the surface which opposes the rolling motion of an object that rolls over it by which it slows down and eventually stops. The other name of rolling friction is the rolling resistance. Factors influencing rolling friction are shape of the tyre ( or wheel ), the type of the surfaces, speed of the wheel and the pressure on the tyre.