Push & Pull are Forces

A force is a

push or a pull.

PUSH is an action

of moving an

object away.

PULL is an action

of bringing an

object towards us.

pressing an

iron

squeezing

a sponge

kicking a

ball

stepping

on a scale

hitting a

nail

poking a

hole in the

donut

cycling

stretching a

spring

dragging a

suitcase

raising a

flag

drawing

back an

arrow on a

bow

pulling a

nail

opening a

door

opening a

can of soda

Push &

Pull

sawing a

wood

rowing a

boat

playing a

violin

scrubbing

the floor

playing a

yoyo

wringing a

wet table

cloth

inflating a

bicycle tyre

Effects of a Force

a force

cannot be

seen but their

effects can be

observed or

felt

can change

the shape of

an object

can change

the motion of

an object

A lump of dough is pressed.

The dough is flattened.

An empty aluminium tin is

crushed. The tin is

crumpled.

A spring is stretched. The

spring extended.

A sugar cane is squeezed

through the rollers. The

sugar cane is flattened.

a force changes

shape of an

object

A Force Changes Motion of an Object

move

a stationary

object

stop

a moving

object

change the

direction of a

moving object

make an object

moves slower

(decelerate an

object)

make an object

moves faster

(accelerate an

object)

The golfer hits the

stationary golf ball.

The golf ball starts to

move.

The hockey player

uses his hockey stick

to stop the ball. The

hockey ball stops

moving.

The player hits at an

angle to the moving

volleyball. The

direction of the

volleyball changes.

An unsporting player

pulls the shirt of his

opponent. This slows

down the movement

of his opponent.

The player pushes the

skateboard with his

foot. This makes the

board move faster.

Friction in Action

Different type of surfaces, produce different amount of friction.

friction

a type of force

(frictional force)

opposes the

motion of an

object

occurs when

two surfaces

rub against

each other

Factors Affecting

Friction

SURFACE

how rough the

surface is

the smoother the

surface is, the

lesser is the

frictional force

WEIGHT

the weight pushing

down on the

surface

the more heavier

the object is, the

greater is the

frictional force

it is easier to pull a

box on a smooth

surface than on a

rough surface

it is easier to pull a

light box than a

heavy box on the

same type of

surface

Effects of Friction

palms warm when

rubbed together

heat produced by

friction causes sparks

produces

heat

tread of tyres worn out

after much use

eraser gets smaller and

smaller after each use

causes wear

and tear

heavy objects cannot be

moved easily

the rolling marbles will

gradually slows down

and finally stops

opposes

motion

an electric drill produces

a loud noise when it

touches the wall

friction between the

bow and the string of

the violin poduce

sounds

produces

noise and

sounds

Ways to Reduce Friction

Ways to Increase Friction

using rollers

using wheels

using ball bearings

using oil, grease

or wax

using talcum powder

air cushion

using sand paper

aerodynamic shape

tread

patterns

spikes and

studs

resin

grooved

floor or

stairs

rubber

material

keeping

surfaces dry

exerting a

greater

force

patterns on shoe

soles and tyres

increase friction

under wet

condidtions

shoes with spikes

and studs give the

wearer a better grip

on the field

resin is applied on

the bow of a violin

to increase friction

between the strings

and the bow

concrete floor that

grooved minimize

slipping

rubber materials

have more friction

than other

materials

dry hands grip a

barbell better

a harder grip on

the rope increases

friction on the rope

Why Friction is Necessary? Or Its Advantages

When Friction is Harmful? Or Its Disadvantages

Prevents us from slipping or skidding.

Makes it possible for things to be held.

Leaves a mark on the paper.

Enables vehicles to move and stop.

Produces enough heat to ignite the match.

Makes the knife fine and sharp.

Friction caused by

air resistance

slows down

motion.

Friction between

skin and cement

floor can cause

painful scrape.

Soles of shoes

wear out due to

friction.

Heat produced by

friction causes

damage to car

engine.

Creates noise

pollution.