Magnetic, electrostatic and gravitational forces

Sometimes forces can move objects without even touching them. Let's find out more about forces at a distance!

Watch this video to find out more about forces that can act on objects without touching them.

Some forces are called contact forces because they happen when things are touching, or in contact with each other. If you push or pull something, you are using contact forces.

Not all forces need things to touch each other to make something happen.

Some objects experience forces from things that are not touching them. These are called non-contact forces.

Here are three non-contact forces:

• Gravitational force: things near the Earth fall toward the Earth unless something holds them up. The Earth pulls any object towards the centre of the Earth without touching it.
• Magnetic force: magnets can be used to make other magnets and things made of iron and some other metals move without being touched.
• Electrostatic force: something that has been electrically charged can make other things move without touching them.

All three of these are non-contact forces because they work at a distance without touching things.

Gravity keeps us on the Earth’s surface and is the reason a ball kicked into the air comes back down.

Gravitational force is a non-contact force that pulls matter (anything you can touch) together. Even your own body has a tiny gravitational force as your body is made of matter.

The more matter something has, the greater the gravitational force it can apply.

This is why you don't really notice the gravitational pull of people, animals and objects around you. It also explains why gravity is stronger on Earth than the Moon.

In 1666, Isaac Newton first came up with the idea of gravity.

It is thought that he was inspired by watching an apple fall from a tree. Newton wondered what force made the apple fall downward instead of moving sideways or simply floating away.

Did you know?

All forces are measured in units called Newtons, named after Sir Isaac Newton.

And we can measure gravitational force using a device called a Newton meter.

Using gravitational force

Gravitational force is what makes hydroelectric power stations work.

Water in a high reservoir is released and falls through pipes because of gravity. The energy of the falling water turns turbines which spin round, generating electricity.

Magnetism is a force of attraction (pull) or repulsion (push) between two metal objects.

It is a non-contact force as the magnets do not have to be touching.

Magnets have an area around them called a magnetic field. They can do things to other objects in this magnetic field.

You can see a magnet's magnetic field by scattering tiny iron filings around it.

The iron filings form a pattern that reveals the lines of the magnetic field. The closer together the lines are, the stronger the magnetic force.

Can you see the magnetic force is strongest at the opposite ends of the magnet?

Using magnetic forces

Magnets do an important job at recycling centres.

Because magnets attract objects that contain iron, for example food tins, but do not attract aluminium, for example drinks cans, they can be used to separate these different metals so they can be reprocessed and reused.

Electrostatic force is a non-contact force and can pull or push on objects without touching them.

Rubbing two materials together makes a negative charge move from the surface of one material to the other material.

As a result, one of the objects will have a positive charge and one will have a negative charge.

This means:

• Objects with different charges (positive and negative) will attract each other.
• Objects with similar charges (positive and positive or negative and negative) will push away from each other.

Electrostatic force is sometimes called static electricity. It is important to remember that static electricity is not the same as electricity in circuits.

Using electrostatic forces

Inkjet printers use electrostatic to create images.

The printer nozzle releases a spray of tiny, electrostatically charged ink droplets. Two charged plates are used to direct the ink drops to the exact place on the paper they are needed to create pictures or letter.

Gravitational force – a non-contact force that pulls matter together.

Magnetic force – a *non-contact force of attraction (pull) or repulsion (push) between magnetic objects and some metals.

Electrostatic force – a non-contact force that can pull objects with different electrical changes together, or push objects with similar electrical charges apart.

Try this electrostatic attraction experiment!

You will need:

• Balloons
• An empty drinks can
• Small pieces of paper
• Access to a cold water tap

In this experiment, you rub a balloon to build up an electrostatic charge. See what this charge does when you bring the balloon near other objects.

Watch this video to find out more about this experiment.

Now you know all about forces at a distance, why not test yourself with our fun quiz!