FORCES

​A force is what makes objects move

There are two types of forces: contact forces and non-contact forces.

In contact forces there is contact between objects. You need to touch them.

In non-contact forces there is no contact between objects. They act at a distance.

CONTACT FORCES

​They use a push or a pull to move objects

They have different effects:

1. Make an object start moving.

2. Make an object stop moving.

3. Make an object change shape.

4. Make an object break.

​CHANGES OF SHAPE

Some objects can change shape PERMANENTLY. They don't go back to their original shape when the force finishes acting on them.

Other objects change their shape TEMPORARILY. They go back to their original shapee when the force finishes acting on them.

A force can make an object stop moving. However, if we let the object move and we don't stop it, it will finally stop. Why? Because of friction.

Friction is a contact force that occurs then two objects rub against each other. The object that doesn't move (= the surface) applies an opposed movement to the moving object and it slows down until it stops.

FRICTION IS A CONTACT FORCE

NON-CONTACT FORCES

​They don't use contact to move objects

There are two types:

1. Magnetism

2. Gravity

​MAGNETISM

Magnetism is a non-contact force produced by magnets.

Magnets have magnetic fields that attract metal objects

Magnets have two poles: North (N) and South (S).

When we put the same poles of two magnets together they repel.

When we put opposite poles of two magnets togehter they attract.

GRAVITY

Gravity is a non-contact force that pulls everything towards the centre of the Earth.

If we drop a ball the force of gravity makes it fall to the ground

Gravity is a non-contact force that pulls everything towards the centre of the Earth

​A) We throw a ball up in the air.

B) It goes up quickly until it stops and the force of gravity makes it fall to the ground.

C) It goes faster until it is on the ground

GRAVITY

A) We drop a ball

B) The force of gravity makes it fall to the ground.

C) It goes faster until it is on the ground.