Levers, pulleys and gears
Simple mechanisms for primary schools
Levers, pulleys and gears appear the in the national curriculum in key stage 1 and key stage 2:
Forces: Recognise that some mechanisms, including levers, pulleys and gears, allow a smaller force to have a greater effect.
Explore and use mechanisms [for example, levers, sliders, wheels and axles], in their products.
Understand and use mechanical systems in their products [for example, gears, pulleys, cams, levers and linkages]
This page offers a brief description of the science behind these simple machines with examples of activities you can try at school or home.
This page is intended to replace our old resource. Simple as that page was, it’s consistently one of our most popular pages. We thought you might like a little more.
Mechanical engineering jobs are all about solving problems and creating products to meet human needs. Work includes solving problems using machines or machinery by designing, testing and improving mechanical devices. Mechanical engineers use a wide range of tools, techniques and machinery in their jobs, which depends on the area of mechanical engineering they trained in and the industry they work in.
Mechanical engineers are curious, self-motivated and hardworking.
A lever is a simple machine which helps us to lift objects. It has a long arm and a fulcrum, which is where the arm pivots. The object you are lifting is called the load, and the force you apply to the arm to make the object move is called the effort. There are three types of lever (see below).
In the TED-Ed video on the right, Andy Peterson and Zack Patterson use the seesaw to illustrate the amazing implications and uses of the lever.
For more examples of everyday uses of levers, click here.
Can you find any levers at school or at home?
The class 1 lever has the fulcrum between the effort and the load, for example when using a hammer claw to remove a nail.
On a class 2 lever, the load is between the fulcrum and the effort, for example when you use a bottle opener or wheelbarrow.
An example of a class 3 lever can be illustrated by using tweezers or tongs where the effort of squeezing the tongs is between the fulcrum or pivot at one end, and the load which is gripped at the other.
You will need 6 lollipop sticks and 4 elastic bands to make your catapult. You will also need something soft to fire, such as a pom pom or mini marshmallow.
Take four of the lolly sticks and place them on top of each
other. Hold them together using an elastic band at each
Using the two remaining lolly sticks, join them at one end
using an elastic band. Put the stack of four lolly sticks in
Use the final elastic band to hold the stack in place. Your
catapult is complete. You can investigate how the position of the stacked sticks affects how well the catapult works.
You will need:
There is a lot more information about how to use this activity as part of a challenge lesson here: Mini-Mangonel
And an instruction sheet to download here.
A pulley is a wheel on a fixed axle with a groove in it to guide a rope or cable. The rope or cable is attached to the object you want to lift and looped over the pulley so that the end of the rope is hanging down on the other side. The pulley changes the direction of the force needed to lift the object or the amount of force that is needed to lift an object.
The video on the right shows how pulleys help us to lift loads. In everyday life they are used in lifts and elevators, in wells for pulling up buckets of water and in weight lifting machines in the gym. Next time you visit a building with a lift, see if you can spot the pulleys working.
With a fixed pulley, the wheel is secured to a single spot. You require the same amount of force to pull the object up as you would if you were lifting it, but the pulley changes the direction of the force. This means that although the object feels as heavy to lift, you can pull it from a much more convenient angle.
With a movable pulley, the wheel moves when you move the load. With this pulley, the direction of force stays the same, but the magnitude of force changes, so the load feels easier to move.
In a compound pulley system, there is a fixed and a movable pulley. This means that you can change both the magnitude and direction of your force. The downside is that you have to do a lot more pulling on the rope!
A complex pulley system contains multiple wheels, which may include more than one wheel per axle with the rope weaving through individual wheels and looping back and forth between wheels of different axles. An example of a complex pulley system is a block and tackle. Complex pulley systems can lift heavy loads by reducing the magnitude of the force. However, a long length of rope is required to achieve this.
You will need:
Follow the video on the right to make your pulley.
Test your pulley to see if it will lift small objects from around the room.
Remember, don’t overload your basket. It is only as strong as the kebab skewer!
Can you build a pulley system to take the Lighthouse Keeper his lunch?
Can you build a pulley system to get tomatoes up and down a mountain without squashing them? Visit the Practical Action website to see the full challenge.
Gears are wheels with teeth that slot together. When one turns, the other turns too. They work in three ways:
Gears allow a small force to have a greater effect.
You will need:
Print out: Gears to print
A4 card to make gears, scissors, glue, split pins, thick card to attach gears to e.g. cardboard box, sharp pencil and sticky tack to make holes.
To make the gears:
Print out the PDF. Stick this to the A4 card and cut out the gears.
Make a hole in the centre of each gear by putting it on top of your sticky tack and forcing the pencil through it.
Position the gears on top of the thick cardboard so that the teeth of one gear are interlocking with the next gear. Mark the position of the centre of each gear using the pencil. Make a hole using the pencil and sticky tack.
Attach the gears to the card using the split pins.
Make a gear chain to create a low gear for cycling up hills.
Make a gear chain to create a high gear for cycling down hills.
Which gear would you choose for cycling on the flat and why? Make this gear chain.
Print off these cards:
Sort the items in the pictures into groups.
How can you categorise them?
You could sort them into items you use in the kitchen, and items that are used elsewhere in the house. Or items that are made of metal, or items that are made of plastic. You can also sort them into items that use levers, pulleys, or gears.
Both types of machines can be described as creating over-complicated machines to solve simple tasks. Building one of these machines as the final activity of a unit on simple machines would be a good challenge for your pupils.
This site from Connections Academy has some useful ideas about what your machines might include or you can watch the video below for inspiration.
All pop up books or cards, whether simple or complex, are made using the same simple mechanisms. If you click here, you will find the instructions for these mechanisms and some more complicated ones.
If you watch the video below you will see how the paper engineer Matthew Reinhart takes these same mechanisms and develops them into speculator pop ups.
Could you develop and improve your basic design into something amazing?
You may want to start by using the basic folds and techniques in your designs. Click here to find the instructions for these mechanisms and some more complicated ones.
You may want to try a ready made pop up. Click here to visit a website with templates, instructions and tutorials designed by a variety of paper engineers.
If you have time, you could watch the tutorial video below to see how to develop your designs into something more complex.