What is a force?

Without forces our world would be silent and immobile. We explain what children learn about forces in Year 3 and Year 5 in the primary-school classroom, and how you can support their learning with hands-on activities and experiments at home.

What is a force?

Everything on Earth is powered by forces, pushes and pulls which act on our bodies and the things around us. Forces make things move and stop moving.

Some of the forces we are subject to are gravity (which keeps us on the Earth's surface), the centripetal force (the force that makes things move in circles) and friction (the force which makes things stick or slide).

Simple machines work by turning small forces into larger ones, allowing us to perform tasks with more strength or speed. Examples of simple machines are levers, gears, pulleys, wheels and screws.

What do children learn about forces in primary school?

Children in primary-school learn that a force is a push or a pull. They will look at different types of forces including gravity, air resistance, water resistance, surface resistance and magnetic forces.

Gravity is the pulling force acting between the Earth and everything on it, for example when you drop something. Gravity pulls objects to the ground. Gravity also holds our universe together, moving the planets in our solar system around the Sun.

Friction is a 'sticking' force – the resistance that a surface or object encounters when moving over another surface or object. Friction both stops and makes things move: it causes things to stick and rub against each other, and also causes slipping and sliding. Air resistance, water resistance and surface resistance are kinds of friction.

Air resistance is the force on an object moving through air, such as a plane moving through the sky. Air resistance affects how fast or slowly objects move through the air; some objects are more streamlined than others, which means the air pulls on them less and they travel faster. A parachute uses air resistance to slow down descent to the Earth.

Water resistance is the force on objects floating on or moving in water.

Surface resistance is the force on objects moving across a surface, such as an ice-skater skating on ice. Grips on your shoes or car tires use friction to stop you slipping. Shiny surfaces have less fiction so they are slippier; rough surfaces have more friction so slow things down.

Magnetic force is an invisible force caused by electrons inside the atoms from which all things are made. Magnetic force controls magnetism and electricity.

Mechanisms or simple machines are tools or equipment such as pulleys, gears and levers. Simple machines can be used to turn a small force into a bigger force; this means we can use these machines to accomplish things more easily. Examples of simple machines are levers (which give us extra pushing or pulling force and help us lift great weights), gears (different-sized wheels which work together and give a machine extra force or speed) and pulleys (wheels and ropes used together to lift heavy objects).

When are children taught about forces in primary school?

In Year 3 children will:

• Explore how objects move on different surfaces
• Investigate magnets

In Year 5 children will:

• Learn what gravity is
• Explore air resistance and water resistance
• Investigate simple machines such as levers, pulleys, gears, wheels and screws and how they allow small forces to have a bigger impact
• Further develop their knowledge of how forces can slow or stop objects moving

How are children taught about forces in the classroom?

Children will learn about forces through a range of experiments. They will plan and carry out tests in small groups, pairs or whole-class situations; examples include:

• How different objects move over a surface (investigating surface friction)
• How a toy car travels over different surfaces (investigating surface friction)
• The best shape and size for a parachute (investigating air resistance)
• Which objects fall to the ground fastest (investigating air resistance)
• Which shape of aeroplane travels most quickly (investigating air resistance)

Children will also observe and explore forces using equipment and examples of simple machines around them. For example:

• Exploring a range of gears, pulleys and levers, looking at how they work and the effect they have on moving objects.
• Exploring examples of friction by looking at different surfaces in the local area or looking at the grip on different shoes.

Activities for at-home learning about forces

• Investigate what objects float and sink in the kitchen sink or the bath and find out about Archimedes' principle.
• Investigate different shapes of paper aeroplanes and which are most effective; discuss why.
• Make a mini-parachute for a teddy. What shape or size is most effective?
• Make a simple pinball machine using a cardboard box and ice lolly sticks and explore the science of forces and motion.
• Why not plan a science day out and visit the Science Museum in London? Before you go, download a Fantastic Forces Trail and a Great Object Hunt (Forces)
• Explore gravity by dropping a selection of objects on the floor – do they always fall? Discuss why.
• Test how a toy car moves down a ramp made of different surfaces or covered in different materials.
• Find out about Leonardo Da Vinci's work with simple machines.