Junior ScienceJunior Science
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
catch and stick to
as a result , creating friction.
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
Synovial fluid in our joints acts as
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
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
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?