### A FLATTENED TYRE STOP SOONER THAN

• Why does the car with a flattened tyre stop sooner than the one with inflated tyres?

Due to flattening of tyres, frictional force increases. Because rolling friction force between the surface and tyre is proportional to area of contact. Area of contact increases for flattened tyres. So rolling frictional force increases and the car will be stopped quickly.

Frictional force:
Opposing force to the body by the contact surface. Due to this friction lot of energy will be wasted. Even then it is a necessary evil. Without this friction we cannot walk, we cannot control the vehicle, etc.

Rolling friction:
Opposing force to the motion of the body when it is rolling is called rolling friction. It is very small among the three kind of frictions. (The three kind of frictions are static friction, kinetic friction and rolling friction)

• Can the coefficient of friction be greater than one?

Answer: Yes. Generally coefficient of friction between the surfaces is always less than one. But under some special conditions like on extreme rough surfaces coefficient of friction may be greater than one.