DELHI TEACHERS’ TRAINING COLLEGE

DEENPUR, NAJAFGARH, NEW DELHI – 110043(Affiliated to G.G.S.I.P. University, Delhi – 110075)

B.Ed. 2015 – 2017Semester - III

Submitted By:- Swati GhanselaEnrollment No.- 05940202115Batch- 2015-17

Made By – Swati Ghansela

MULTIMEDIA MULTIMEDIA LESSON PLANLESSON PLAN

(FRICTION)(FRICTION)

General Objectives:-

i) To enable the students to understand the concept of Science

ii) To develop the logic and reasoning power of the students

iii) To arouse the interest of the students in the quantitative side of the world

Specific Objectives :-

1.Cognitive domain

(a) Knowledge level

The students will be able to

i. define friction

ii. list the types of friction

(b) Understanding level

The students will be able to

i. explain the effect of friction

identify the state of object after application of friction

Name of the School: BVM Public SchoolClass: 8th Subject: Science

Lesson PlanTopic: Friction

(c) Application level

The students will be able to illustrate the effects of friction with example

(2) Affective Domain

The students will be able to acknowledge and associate the learning with real life.

(3) Psychomotor Domain

The students will be able to write the conditions when friction is useful and unuseful

Statement of Aim:-

Today we are going to study the concept of friction

Teaching Aid:- Power point presentation

Previous Knowledge:- Students are aware of force

Recapitulation:- Formula of Area of cube, cuboid

Volume of cube ,cuboid

Homework:- Solve 5 questions each related to area, perimeter from your textbook.

FORCE OF FRICTION Force of friction is the force which opposes the motion of an object over a surface. The force of friction acts between the object and the surface. Friction is caused by the irregularities on the two surfaces in contact. Irregularities on the two surfaces lock into one another. When we attempt to move any surface,

we have to apply a force to overcome interlocking.

Example :- A ball rolling on ground gradually slows down and comes to

rest due to force of friction between the ball and the ground.

If we stop pedaling a bicycle, it gradually slows down and comes to a stop due to force

of friction between the wheel and the road.

INTRODUCTION

Introducing Friction

FACTORS AFFECTING FRICTION

Friction depends upon two factors. They are :-

i) Nature of the surfaces in contact. ( The smoothness of the surfaces).

ii) How hard the surfaces press together.

Friction is less on a smooth surface.

.

Friction is more on a rough surface.

On rough surfaces, there are a larger number of irregularities. So the force of friction is greater if a rough surface is involved.

Activity:-1.Place a book on table.2.Push a book on table.

Observation:-After sliding few distance the book stopped.

Result :- Friction opposes relative motion between the surfaces of the book and the table

Friction is more if the surfaces are

pressed harder…………….?

Friction is less if the surfaces are

not pressed harder…………..?

CAUSE OF FRICTION

Friction is caused due to the interlocking of irregularities between the

two surfaces in contact.

Smooth surfaces have minute irregularities between the two surfaces.

Rough surfaces have larger irregularities between the two surfaces.

So force of friction is more if the surfaces are rough.

TYPES OF FRICTION There are three main types of friction. They are static friction, sliding friction and rolling friction.

a) Static friction is the friction exerted on a object at rest. .

b) Sliding friction is the friction exerted when an object slides over a

surface.

c) Rolling friction is the friction exerted when an object rolls over a

surface.

Sliding friction is slightly less than static friction.

Rolling friction is less than sliding friction and static friction.

Static friction Sliding friction

Rolling friction

FRICTION IS SOMETIMES USEFUL

Friction is useful for many of our daily activities.

Friction between the feet and ground helps us to walk on the ground.

It is possible to write with a pen or pencil on a paper due to friction between

the pen or pencil and the paper.

It is possible to write on a blackboard due to the friction between the chalk and black

board.

Friction between the tyres and the road helps automobiles to move on roads.

Friction between the bricks helps in the construction of buildings.

For holding a glass

For walking To write on board

For construction

Friction Between Pen & Paper For driving

FRICTION IS SOMETIMES UNDESIRABLE

Soles of shoes wear out due to friction. Tyres of bicycles and automobiles wear out due to friction. Steps of staircases and foot over bridges in railway stations wear out due to friction. Knives and razors lose their sharp edges due to friction.

INCREASING FRICTIONFriction can be increased by increasing the roughness of the surfaces in contact.

Eg :-

1.The soles of shoes are grooved to have a better grip on the floor.

2.The tyres of vehicles are treaded to increase the grip on the road.

3.The break pads of vehicles are rough to stop moving vehicles when the breaks are applied.

4.Gymnasts apply some coarse substance on their hands for a better grip.

REDUCING FRICTIONFRICTION CAN BE REDUCED BY :- Using lubricants like powders or oils and grease. Using rollers or wheels. Using ball bearings. We sprinkle powder on a carrom board to reduce friction. Oil or grease is applied between moving parts of machines to reduce friction. Rollers are used in luggage bags to reduce friction. Wheels are used in vehicles to reduce friction. Ball bearings are used in ceiling fans, bicycles and vehicles to reduce friction.

FLUID FRICTIONFluid friction is the force of friction exerted by liquids and gases on objects moving through them.

Fluid friction depends upon :-

1.The speed of the object.

2.Shape of the object.

3.The nature of the fluid.

Example:-Birds flying in air have streamlined body to reduce fluid friction.Fishes living in water have streamlined body to reduce fluid friction.Aeroplanes and spacecraft have streamlined body to reduce fluid friction.