SIMPLE MACHINE

It is defined as a mechanical device that transforms the movement produced by a force, to another movement with a force different from the first, but that performs work in a more advantageous way. For this, it modifies the magnitude, direction and sense of the original movement.
Simple machines work under the principle of the law of conservation of energy (Energy is not created or destroyed, but transformed).

Some of the simple machines are: The lever, the wheel, the inclined plane, the simple pulley, the wedge among others.
We will begin by explaining the simple machine known by the lever.

The lever is a rigid bar that can rotate around a fixed point, called a fulcrum.

If the weight applied at point "B" is called Resistance y is equal to R = 3Kg, the distance from point "0" to "B" is called L1 and if the weight applied at point "A" is called Power and it is equal to 1Kg, the distance from point "0" to "A" we call it L2. For the bar to be in balance, it must be fulfilled that:

Power x L2 = Resistance x L1
P x L2 = R x L1

Where: Power x L2 = Moment of the Power with respect to the point of support.
Resistance x L1 = Moment of Resistance with respect to the point of support.

The equilibrium equations above can be expressed as a function of the moments:
Moment of Power = Moment of Resistance

Of which it is convenient to take an arm (L2) of greater length of the power to be able to raise greater resistance.

"Give me a foothold and I will move the earth"

More than two thousand years ago, in an ancient city of Italy called Siracusa lived an extraordinary character called Archimedes considered one of the first physicists in history, as well as a mathematician, inventor and military engineer. He built many machines to keep his enemies away. Until one day at last the Romans managed to enter the city and killed him when he tried to protect his inventions by covering them with his own body. We have already seen that with a bar with a long enough power arm we can raise large weights applying very little force, for this we would need a point of support. Archimedes said: "Give me a foothold and I will move the earth".

References:
https://maquinas-simples2.webnode.es/nosotros/
Enciclopedia practica Jackson. W.M. JACKSON Inc. Editores.