1. Outcome 4.6
Stage 4
FORCES

2. overview 1) What is a force? Examples of forces Measuring forces
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1) What is a force?
Examples of forces
Measuring forces
2) Contact forces
3) Non-contact forces
4) Balanced Forces
5) Unbalanced Forces

3. Nothing moves by itself. Objects must be pushed or pulled!
what is a force?
A force is a…
…or a…
Nothing moves by itself. Objects must be pushed or pulled!

4. We use forces every day! Action Push and/or Pull? Pressing a button
Climbing a tree
Jumping
Walking
Towing a car
PUSH
PULL
PUSH
PULL
PUSH & PULL

5. What changes happen when forces are applied?
Moving a stationary object
Stopping a moving object
Changing the direction of an object
Changing the speed of an object
Changing the shape of an object

6. How do we measure a force?
Forces are measured in Newtons, written as N for short
Forces are measured using a Force Meter, which uses a spring
The bigger the force, the more the spring stretches
Or, we can calculate it using this equation:
Force = mass x acceleration

7. Forces can happen between objects………...
…by touching
(contact forces):
Frictional force
…or from a distance
(non-contact forces):
Electrostatic force
2) Magnetic force
3) Gravitational force

8. Forces normally occur in pairs………
These pairs are called Action and Reaction
The Action force causes a change
Example: car tyres push backwards on the road to move the car forwards
The Reaction force is the force that ‘reacts’ to the action force.
Example: the road pushes forward against the cars tyres

9. Forces normally occur in pairs………
Action and Reaction forces act in OPPOSITE directions
They can be BALANCED or they can be UNBALANCED