Forces & Simple Machines
Explore how forces make things move and how simple machines help us do work with less effort.
Understanding Forces
A force is a push or a pull that can make an object start moving, stop moving, speed up, slow down or change direction. Forces are measured in Newtons (N), named after Sir Isaac Newton.
Contact Forces
Forces that require objects to touch each other.
- Push -- Kicking a footy moves it forward
- Pull -- Pulling a wagon towards you
- Friction -- The grip between your shoes and the ground that stops you sliding
Non-Contact Forces
Forces that act without objects touching.
- Gravity -- Pulls everything towards the centre of Earth
- Magnetism -- Attracts or repels certain metals
- Static electricity -- A balloon rubbed on your hair sticks to a wall
Amazing fact: Gravity is the force that keeps us on the ground and keeps the Moon orbiting Earth. Without gravity, everything would float away into space!
Six Simple Machines
Simple machines make work easier by changing the direction or amount of force needed. They do not have engines or motors. There are six types of simple machines.
Lever
A bar that rests on a fixed point (fulcrum). Examples: seesaw, crowbar, wheelbarrow.
Pulley
A wheel with a rope that changes the direction of a force. Examples: flagpole, blinds, cranes.
Inclined Plane
A flat surface tilted at an angle (ramp). Examples: wheelchair ramp, slide, loading ramp on a ute.
Wedge
Two inclined planes joined together to split or cut things. Examples: axe, knife, doorstop.
Screw
An inclined plane wrapped around a cylinder. Examples: jar lid, bolt, drill bit.
Wheel & Axle
A wheel attached to a rod (axle) that reduces friction. Examples: bicycle wheels, doorknob, skateboard.
How Simple Machines Make Work Easier
Simple machines help by reducing the amount of force you need to apply or by changing the direction of the force. They do not reduce the total amount of work -- they just make it more manageable.
Lever in Action: The Seesaw
Effort (your push)
You push down on one end of the lever
Fulcrum (the middle)
The fixed point the lever rests on
Load (the heavy object)
The other end lifts up with less effort than lifting directly
Real-Life Australian Examples
Ramps on Sydney ferries: Inclined planes let passengers with wheelchairs and prams board easily.
Cranes at construction sites: Use pulleys to lift heavy steel beams high into the air.
Farm gates: Use levers and hinges to open and close with minimal effort.
Key Vocabulary
Force
A push or pull that can change an object's speed, direction or shape. Measured in Newtons (N).
Friction
A force that opposes movement between two surfaces that are touching. It slows things down.
Fulcrum
The fixed point on which a lever rests or pivots. The position of the fulcrum affects how easy it is to lift a load.
Simple Machine
A device with few or no moving parts that makes work easier by changing the force needed or its direction.
Worked Examples
Why is it easier to push a heavy box up a ramp than to lift it straight up?
Step 1: A ramp is an inclined plane, which is a type of simple machine.
Step 2: The ramp spreads the lifting effort over a longer distance, so you need less force at any moment.
Answer: The ramp reduces the amount of force needed by increasing the distance over which you push, making the job feel easier.
Identify the simple machines in a wheelbarrow.
Step 1: The handles act as a lever. You push down on one end to lift the load at the other.
Step 2: The front wheel is a wheel and axle that reduces friction and makes it easy to roll.
Answer: A wheelbarrow contains at least two simple machines: a lever (the handles) and a wheel and axle (the front wheel).
What is the difference between a contact force and a non-contact force?
Contact forces require objects to be touching (e.g. pushing a door, friction between tyres and road).
Non-contact forces act at a distance without touching (e.g. gravity pulling you down, a magnet attracting a paperclip through air).
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
A seesaw on the playground is an example of which simple machine?
Question 2
Which force pulls everything towards the centre of Earth?
Question 3
A wheelchair ramp is an example of which simple machine?
Question 4
What is the fixed point that a lever rests on called?
Question 5
Which of these is a non-contact force?
Key Concepts Summary
- ●A force is a push or a pull that changes how an object moves.
- ●Contact forces (push, pull, friction) require touching; non-contact forces (gravity, magnetism) act at a distance.
- ●The six simple machines are: lever, pulley, inclined plane, wedge, screw, wheel and axle.
- ●Simple machines make work easier by reducing force needed or changing force direction.
- ●Many everyday objects (wheelbarrows, ramps, scissors) combine multiple simple machines.