The lever principle is also called the "lever balance condition". To balance the lever, the magnitude of the two forces acting on the lever (force point, fulcrum and resistance point) is inversely proportional to their moment arms. Power × Power arm = Resistance × Resistance arm, expressed in algebra as F1·?l1=F2·l2. In the formula, F1 represents power, l1 represents power arm, F2 represents resistance, and l2 represents resistance arm. As can be seen from the above formula, To make the lever reach balance, the power arm is several times the resistance arm, and the power is a fraction of the resistance.

When using a lever, in order to save effort, you should use a lever with a power arm longer than the resistance arm. ; If you want to save distance, you should use a lever whose power arm is shorter than the resistance arm. Therefore, using a lever can save effort and distance. However, if you want to save effort, you must move more distance; if you want to move less distance, you must Spend more effort. It is impossible to save effort and move less distance. It is based on these axioms and based on the "center of gravity" theory that Archimedes discovered the lever principle, that is, the "double When objects are balanced, their distance from the fulcrum is inversely proportional to the weight. The fulcrum of the rod does not have to be in the middle. A system that satisfies the following three points is basically a lever: fulcrum, force application point, and force receiving point. The formula is as follows Writing: power The functions are different. For example, there is an air pump that is stepped on by foot, or a juicer that is pressed by hand. It is a labor-saving lever? (force arm? >? force moment); but we need to press a larger distance to bear force. There is only a small movement at the end. There is also a kind of laborious lever. For example, on the roadside crane, the hook for fishing is at the tip of the entire rod, the tail end is the fulcrum, and the middle is the hydraulic press? (torque? >? moment arm), this is It is a laborious lever, but the result of laboriousness is that as long as the middle force application point moves a small distance, the tip hook will move a considerable distance.? Both levers have their uses, but they need to be evaluated where they are used to save effort. Or to save the range of motion. There is another thing called an axle, which can also be used as a lever, but the performance may sometimes require calculation of rotation. The ancient Greek scientist Archimedes has this saying that has been passed down through the ages. His famous saying: "If you give me a fulcrum, I can lift the earth." This sentence is not only an inspiring aphorism, but also has a strict scientific basis.