Force is like an invisible push or pull that makes things start, stop, speed up, slow down, or change direction.

• When you kick a ball — that’s force!
• When you open a door — that’s force!
• When wind pushes your kite up — nature is using force!

We described many types of force here.

Force is a vector quantity.
If you don’t remember what that means, check out our article on vectors.

To represent a force, we use an arrow called a vector. This arrow shows both the size (also called magnitude) and the direction of the force.

The direction of a force is really important.
In the example below, both forces have the same size — but they’re pointing in different directions, so they are not the same force:

The length of the arrow tells us how strong the force is.
A longer arrow means a bigger force.

We measure force in Newtons (N).
You’ve probably heard the story of Isaac Newton discovering gravity when he saw an apple fall from a tree:

And here’s a fun fact:
A force of 1 Newton is about the force of a medium-sized apple falling to the ground!