# What is Friction?

### The story of Fire

Long long ago the early man did not know what fire is. They ate raw flesh and raw plants. They used to hunt animals and feed on them without cooking, which is very unhealthy and made the early man’s sick. Until one day!

One day an early man was playing with 2 sticks, he held both of them and was playing with them by rubbing them against each other. He was playing for a very long time and as he rubbed the sticks against each other slowly smoke came from them.

Early man did not understand what was happening. He kept rubbing them. Then suddenly fire came out of the sticks and the sticks were on fire, the early man did not know what this orange thing was. He tried to touch it. It was very hot and his hand got burned.

Soon other early man’s came to that place and observed it. They tried to do this with other sticks. Even then there was a fire.

The early man studied the fire and soon learned to cook food. And today we know everything about the fire.

What made the creation of fire by that early man?

1. The early man had powers
2. The rubbing of the sticks
3. God gave fire for early man to play
4. The stick had some magic

### Activity

Try to rub both of your hands really fast and observe.

We rub our hands in the winter season often because it is very cold outside and we want to feel some warmth.

Why do you think your palms get warm when rubbed against each other?

## Friction

The palms got warm because of friction and the fire was produced by early man because the friction between the sticks produced very much heat and it led to the fire.

So, what is FRICTION?

Friction is a force that does not allow one object to rub against the surface of others. Friction is a surface force. This force is opposite to the movement of the object on the surface, which means it does not allow the movement. And the energy put into the object for rubbing gets converted into heat.

When the stick was rubbing against another stick. Both were opposing the movement of the other. The energy that the early man was putting into the sticks for rubbing them got converted into heat and it gave fire.

Why does the Frictional force exist?

Every object that we see is not as soft as we think it is. When we look very very closely at the object we can see that the surface is not smooth but rough. This roughness of surfaces is what causes friction.

Uses of Friction

There are so many uses of friction. The reason we are able to hold any object in our hands is because of friction. The roughness our hands have because of the presence of fingerprints helps us hold objects.

Fun fact

If we did not have fingerprints, we cannot hold Glass. The friction between our fingerprint and the glass is what allows us to hold it ‘firmly’.

Friction creates heat and in large machines when one surface rub to others it creates so much heat and the machine is damaged. That is why we should reduce friction.

How Friction can be reduced?

Frictional force can be reduced when it is producing so much heat and is not helping. And we can do that by applying something called a Lubricant. Lubricant is an oil that smoothens the surface. When the surface is smooth the is no Friction and there is no heat.

### Quiz

1 ) What is friction

• Friction is the name of a bird
• Friction is a force
• Friction is heat
• Friction is another name for speed

2 ) When two surfaces rub against each other heat is produced because of friction. (            )

• True
• False

3 ) When one wooden block is rubbed against another. It is hard for the block to move. What is slowing down the movement?

• Softness of wood
• Friction between them because of rough surface
• It is not hard to rub two wooden blocks
• The wooden blocks don’t like each other

4 ) Rubbing your hands together creates _____.

• Water
• Gravity
• Mass
• Heat

5 ) Which of the following is NOT an example of friction as a helpful force?  (select all the answers that are correct)

• Using your hand to wave hello to a friend
• Using a cloth to clean a pair of glasses
• Using a marker to draw a picture on paper
• Using a scrub brush to wash dishes

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