FRICTON

Suppose you decide to ride a skate board

You push off the ground and start moving

According to Newton’s second law

of motion ,if no

other forces are acting

on your skateboard , you

will continue to move….BUT

The reason is that there exist a forcebetween theground and lower portion of the

skateboard, calledFRICTIONAL FORCE.

Friction is the force which opposes relativemotion

between two surfaces in contact with eachother

Even though a surface may look smooth, if you magnify thesurface it isn’t smooth.Everything is made of molecules. The molecules cometogether to make bumps. Some surfaces have moleculesthat leaves large bumps and some leaves small bumps.Micro welds occur when two bumpy surfaces are rubbedup against each other they stick together.

Static frictionFrictional force between two surfaces before there is a relative force between the surfaces in contact.

Kinetic friction It is the force of friction which calls in to play when there is relative force between the surfaces.

Helps us in walking conveniently. It save us from

slipping.

Helps us in writing on piece of paper.

Helpful in eating and drinking

Lighting a match stick by rubbing.

Nails and screws join two surfaces due to the

friction.

we can not climb a tree.

Trains can run on the rails.

In fact life become impossible if there is no friction

in nature.

Due to friction the whole energy given to a machine is not converted in to useful work; a portion of energy is wasted to overcome friction.This reduces the efficiency of the machine. The energy used in overcoming friction appears as heat. Moreover, friction causes wear and tear of the moving parts of the machine due to rubbing.

It is not possible to walk or drive through muddy

and slippery roads. For this sand and gravels are

spread to reduce friction

Tyres of our vehicles also the soles of the shoes are

grooved.

Mountaineers also wear spiked shoe.

To overcome skidding along a slippery surface we adopt

measures to increase friction.

•Reduce the area of contact of two surfaces.

•Making the surfaces as smooth.

•Lubrication can reduce friction.

•Using ball bearings.