A lever allows you to lift heavy objects using less force by acting as a fulcrum, with your arm bone serving as the lever itself when picking up heavy objects. By around 200 BC, scientists such as Archimedes started to understand why levers worked by using mechanical advantage to make tasks easier. A screw is also a type of lever that uses the same mechanical principles.

2.  Whenever you pick up anything heavy
your arm bone acts as the lever itself.

3.  By about 200 BC scientists like
Archimedes were beginning to figure out
why levers worked.

4. A screw is a lever.