How Levers, Pulleys and Gears Work

For thousands of years mankind has been perfecting the art of lifting heavy things, manipulating the laws of physics using nothing more than a few simple tools and a bit of ingenuity to allow huge loads to be moved very easily. This is only possible because cleverly designed machines like this pulley system are able

to amplify forces in some way. The amplification of a force is called mechanical advantage, and we can quantify the amount of mechanical advantage a specific system can generate as the force that is output by the system divided by the input force. To illustrate this consider a mass of 100 kg. To lift it off the ground you need to apply a force of around 1 kN.

But if you use a device with a mechanical advantage of 2, you only need to input a 0.5 kN force. To explain how this is even possible, this video will take a look at three devices - levers, pulleys and gears - that are able to do just that. I've also covered a fourth way of generating mechanical advantage, using hydraulic systems,

in a companion video that you can watch right now over on Nebula. The best way to get access to Nebula is by signing up to our bundle deal with this video's sponsor CuriosityStream, but more about that later. Let's start with the lever. Consisting of just a beam pivoting about a fixed hinge, called the fulcrum, it's one

of the simplest ways of generating mechanical advantage. Consider the amount of force we need to balance a mass located at one end of the beam. When discussing levers it’s common to talk about a load, which in this case is the mass, and an effort, which is the force that needs to be applied to lift the load.