Concepts

Class 8
Chapter 12 Class 8 - Friction

## Why is friction a necessary evil?

It is both good thing and bad thing for us

## Why friction is necessary? (Advantages of Friction)

Or we can also say, what are the different uses of Friction

Friction is used to-

### Help us walk without slipping

Friction helps in walking on the ground because friction between our soles and ground prevent us from slipping

Walking on slippery ground is difficult because friction is less there. So, we may slip

### Make Moving objects Stop

If there is no friction

An object which starts moving, it will never stop

### Picking and Holding Things

We would not be able to pick or hold a thing as it would slip from our hands

### Helps in Writing

We are able to write because graphite particles from our pencil rub off on paper due to friction

Similarly teacher is able to write on board because chalk powder rubs off on board due to friction

If there is no friction, we would not be able to write

### Lighting a matchstick

When we rub matchstick with side of matchbox,it produces heat due to friction.Without friction,we would not be able to light fire

### Fixing a Nail in Wall

When we hammer a nail in wall, friction is produced between surface of nail and wall.

This friction helps in holding surface of nail properly

## Why friction is evil? (Disadvantages of friction)

### It wears out different products

Example

When we wear shoes,soles wear out after some time because of friction

Steps of bridges wear out because of friction

Ball bearing of machines wear out due to friction

Tyres of car wear out after some time due to friction

### It increases heat which may damage machines

When we use machines for a long period,it gets heated up

This is because of friction produced

Thus friction helps in heating of machine which may damage them

### Friction Slows down speed of Object

Since friction opposes motion,it slows down speed of motion

Without friction,vehicles would move faster

### Friction Reduces Efficiency and Increases Costs

Because of friction,more fuel is required to run vehicles like car

Hence it increase costs of operating vehicles and reduce their efficiency