Concept of Friction

‘The Concept of Friction Explain the concept for friction table ifthe block is to be moved along the table. Weight the two contacting surface. The friction between two surfaces exists because of the nature of the surface of the bodies in Demonstration The peak and valleys on the surfaces of bodies may be due to a random arrangement of coarse particles, for example the surface of griding stones.

‘The Advantages and Disadvantages of Friction in Daily Life Realize the advantages and disadvantages of friction n day life

Advantages of Friction

Thefrction force has several advantages which includes the following

• Ithelps in walking process (because fiction fore stop us from slipping over)

and the road surface

• it helps in car braking system, Brakes rely on friction between the brake drum oc pads

and the wheels. In a bicycle, there are brake pads which lamp onto the wheel to slow it down

Disadvantages of friction

2 ‘Cause machinery to be less efficient.

Methods of Reducing Friction

‘Theiferent methods ofreducing friction between surfaces includes the following 1 Polishing:Polishing the surface, reduces the iregularites and hence, reduces friction

• —_Lubricatiom:t provides a layer of the lubricant on which the bodies can easly slide
• Use of ball-bearing or roller bearing:Roller becring help to conver sliding ftition into a
• Streamfining:Fast cars, boats, planes efc., have a streamlined body. This is to allow air (or

Roller . Iisa simple cylinder on which a body to be pulled RESTS. . It is used to climinates sliding friction. . Conveyor belts use metal rollers. ees (y ) OX) ae, AN Wheels

Types of Friction

‘Types of Friction Identify types of friction There are three main types of friction in daily life which include the following

• Static fiction: an opposing forcebetween two solid objectsat rest In simple words, when

there is no relative motion between two solid objects in contact with each other, we describe the frictional force between them asstatic. body just move over another.

• Dynamic friction: numerically equal to the foree of opposition when a body’ is moving

Limiting Friction

one another. Is the maximurm possible value of stati friction. Iti the frictional force that must surface.

Example 1

A block of mass 20 kg is pulled along a horizontal surface. If the coefficient of friction is 0.4,

Solution

Laws of Friction

Laws of Friction

The five laws of friction . When an abject is moving, the friction is proportional and perpendicular to the normal farce (8).

• Friction is independent ofthe area of contact.
• Within rather lange limits kinetic friction is independent of velocity

The Coefficient of Friction

Determine the coefficient of friction the normal reaction, R. Bak R

Types of Coefficient of friction

There are three main types of coeficient of fictions which includes the following Us=FreR Coofficiet of dynamic fiction Us Ud=FaR Laws of Friction in Solving Problems Apply laws of friction n solving problems Demonstration to determine coeflicient of dynamic friction.

Method of calculation

The coefficient of dynamic friction U is

U- Frictional foree, Fy/Normal Reaction, R

U= FUR ()

By Resolving farces we get

Fr=W Sind ay

R= W Cos _ amy Put Eqa (i) ad (i nto eqn ()

U=W SinQ”We 030

U=W SinQ”WCos0

But SinQiCosQ=TanQ

U=TanQ Thus

But U=Tang = (abvebj

Example?

eS — Coefficient of static friction, Us:

At Equilibrium

U=WSinQiwCosQ

U= W/W) (SinQ/CosQ)

x