Junior ScienceJunior Science

FrictionFriction

What is Friction?• Friction is a force which

prevents easy movement between objects.

• Friction opposes motion.

What causes Friction?Friction is caused by the fact that all

surfaces however smooth will have tiny lumps and hollows in their surface.

On a microscopic level, the surface of

most materials is

quite rough.

The surfaces

catch and stick to

one another

as a result , creating friction.

Surface A

Surface B

Friction all around us!

Types of Friction

There are three basic types of friction

Dry Friction Fluid Friction Rolling Friction

Types of Friction – Dry Friction

Dry friction resists the motion of two solid surfaces in  contact.

Dry friction is divided into static friction between non-moving surfaces, and kinetic friction between moving surfaces

Types of Friction – Fluid Friction

Fluid friction is a kind of friction that occurs in fluids that are moving

relative to each other.

Types of Friction – Rolling Friction

A Rolling friction is a resistive force that opposes the rolling motion of an object. Rolling friction occurs

when a round object rolls around a surface.

Lubricants Lubricants such as oil

are used to reduce friction between

moving parts.

Synovial fluid in our joints acts as

a lubricant.

Friction Good or Bad?

Friction prevents movement.

Friction can waste a lot of energy as objects try and overcome the force of friction.

Friction wears away surfaces in contact

Friction generates heat which can have both positive and negative effects

Friction enables movement (walking, Running)

Friction enables every day activities such as walking and writing

You are walking on the street and you walk onto ice.

Does the friction between your

shoes and the ice

a. Increase b. Decrease

If so.....why can ice skaters move on ice?

The sharp blades on the boots cut into ice when placed side on

to the ice.

For the skater to move the blade is turned forward and the skater pushes to move.

This cutting increases the friction between

the blade and the ice.

A car engine has many moving

metal parts. These parts need to slide

easily past each other.

What could be done to reduce friction and stop them rubbing?

ensure that the metal parts are smooth.

use oil to make sure that the surfaces slide easy, reducing heat and thus

preventing wear.

Summary• Friction is a forceforce between two

surfaces. • Smooth surfaces have less

friction. • Rough surfaces produce more

friction. • Friction causes heatheat. • We can reduce friction by using

liquids to make surfaces smoother.

The brakes on a bike work by using

friction. The rubber pads presses on the

rim of the wheel and the friction slows down the

wheel.

Do you expect the brakes to be

a. Hotb. Cold

Friction causes heatheat

Which surface has got the

most friction between your shoes and it:

a. A dry tiled floorb. A tiles floor with a water spill?