Friction

Contents

Key Stage 2

Meaning

Friction is a force that slows things down when two surfaces are touching each other.

Singular Noun: Friction

Plural Noun: Friction

About Friction

Friction can only happen when two surfaces are touching so it is called a "Contact Force".

Friction depends on the texture of a surface.

The rougher a surface is, the more friction an object will experience when it is moving.

The smoother a surface is, the less friction an object will experience.

A surface could be described as high friction or low friction.

Sometimes a low friction surface is called "slippery".

Experiments

Friction and Shoes

Good shoes are designed to have a high friction surface on the sole. Take off one of your shoes and look at the bottom of your shoe with a magnifying glass.

You might try to answer the following questions:

• Who has the slipperiest shoes and how do slippery shoes look different from shoes that are not slippery?
• When shoes get older, how does the bottom of the shoes look different and do shoes get more slippery or less slippery as they get old?

Friction of different surfaces

1. Take a flat piece of wood and attach spring to one end.

2. Pull the piece of wood by the spring along the carpet and measure how long the spring is as you drag it.

3. Repeat this by dragging it along a table and the tarmac outside.

4. Write down which surface made the spring go longest. That is the surface with most friction.

Key Stage 3

Meaning

Friction is a force that acts to slow an object down when two solid surfaces are in contact.

About Friction

Friction is a force so it is measured in Newtons.

Friction is a contact force because it only exists when two surfaces are touching.

Friction occurs because two rough surfaces have bumps that fit together resisting the motion of an object.

The two diagram shows two rough surfaces and two smooth surfaces. The friction between the rough surfaces is greater because there are more bumps in the way to prevent the surfaces sliding against each other.

Examples

Friction acts at the point where the bowling ball touches the ground. The force of friction acts to decelerate the bowling ball as it moves.	Friction acts at the point that the tyres touch the ground. The force of friction can act to decelerate the car but can also be use to accelerate the car. If there was no friction the wheels would spin but the car would not accelerate.