1. Friction
Junior Science

2. What is Friction?
Friction is a force which prevents easy movement between objects.
Friction opposes motion.

3. On a microscopic level, the surface of most materials is quite rough.
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

4. Friction all around us!

5. Types of Friction There are three basic types of friction Dry Friction
Fluid Friction
Rolling Friction

6. 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

7. Types of Friction – Fluid Friction
Fluid friction is a kind of friction that occurs in fluids that are moving relative to each other.

8. 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.

9. Synovial fluid in our joints acts as a lubricant.
Lubricants
Lubricants such as oil are used to reduce friction between moving parts.
Synovial fluid in our joints acts as a lubricant.

10. Friction Good or Bad? Friction enables movement (walking, Running)
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

11. You are walking on the street and you walk onto ice.
Does the friction between your shoes and the ice
a. Increase
b. Decrease
The friction between your shoes and the ice decreases (there is less friction) that is why your feet slip.

12. 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.
This cutting increases the friction between the blade and the ice.
Ice skaters wear special boots that have a sharp blade on the bottom of each boot.
For the skater to move the blade is turned forward and the skater pushes to move.

13. What could be done to reduce friction and stop them rubbing?
ensure that the metal
parts are smooth.
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? 1.
use oil to make sure that the surfaces slide easy, reducing heat and thus preventing wear.

14. Summary Friction is a force between two surfaces.
Smooth surfaces have less friction.
Rough surfaces produce more friction.
Friction causes heat.
We can reduce friction by using liquids to make surfaces smoother.

15. Do you expect the brakes to be
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. Hot
b. Cold
Friction causes heat

16. Which surface has got the most friction between your shoes and it: a
Which surface has got the most friction between your shoes and it: a. A dry tiled floor b. A tiles floor with a water spill?
The dry wooden floor has got the most friction. This is why people put signs up when floors are wet because there is less friction on the surface for your shoes to grip.