Q.What is Air Resistance?

Friction Types and Examples

Every sport depends on friction, whether or not an athlete ever thinks about it. A sprinter's spikes gripping the track, a gymnast's chalked hands on the bars, a hockey stick's grip tape — all rely on the same underlying force. Physical Education classifies this force into five specific types, each with its own role in sport.

The Five Types

Static friction exists before an object starts to slide — it is present whenever contact between two surfaces is not yet moving relative to each other. A batsman's hands gripping the bat before the swing, or a rock climber's static hold on the rock face, both rely on static friction.

Kinetic (sliding) friction is created once an object actually starts sliding across a surface — a skater's blade sliding across ice, or hands rubbed together to generate warmth.

Rolling friction occurs when one surface rolls over another, such as a ball rolling along the ground or a ball bearing turning inside a wheel. It is generally much smaller than static or kinetic friction between the same surfaces.

Fluid friction is the resistance a body experiences moving through air or water — also called air resistance or water resistance. A swimmer pushing through water, a sky-diver falling through air, and a discus or javelin travelling through the air during flight are all affected by fluid friction, as is a high jumper's body moving over the bar.

Limiting friction, a more recently recognised category, is the force that comes into play at the exact moment a body is on the verge of moving over another surface — the maximum static friction reached just before sliding begins.

How Sport Uses Friction Deliberately …