Levers
Levers are very simple mechanical engineering devices.
A lever consists of a beam or rod, which pivots on a fulcrum. The purpose is to to lift weights with less effort.
A good example of a lever is children on opposite ends of a seesaw, lifting each other's weight up and down. Another example is using a board to pry something loose.
Download the slides for this video (6.3 MB), or the slides for any of the other videos on 'Mechanical Engineering Components'