Mozi first put forward the principle of leverage in the Warring States Period, and said in Mozi Xia Jing that "balance must be positive, which is called gain"; "Balance, heavier than its side, will be beaten. If the weights are not similar and the scales are balanced, then the length of the bid is short. If the weights are similar, the bid is lower than and the bid is won. " There are equal arms and unequal arms inside; Some change the weight of both ends to make it biased, and some change the length of the two arms to make it biased.
Archimedes also put forward the lever principle in the book The Balance of Plane Figures. He first regarded some empirical knowledge in the practical application of leverage as "self-evident axioms", and then proceeded from these axioms, applied geometry, and obtained the principle of leverage through strict logical argumentation.
Extended data
The concept of lever principle:
Using lever can save manpower and distance. However, if you want to save energy, you must move more distance; If you want to move a shorter distance, you must work harder. It is impossible to save energy and move the distance. The fulcrum of the lever does not have to be in the middle. A system that satisfies the following three points is basically a lever: fulcrum, force point and force point.
The formula is written as follows: power x power arm = resistance x resistance arm, which is a lever. Levers also have labor-saving levers and labor-saving levers, which have different functions. For example, there is an air pump with feet or a juicer with hands, which is a labor-saving lever; But we have to press down for a distance, and the stressed end only moves a little.
There is also a laborious lever. For example, the crane on the roadside, the fishing hook is at the tip of the whole pole, the fulcrum is at the end, and the hydraulic press is in the middle (torque >; Arm of force), this is a laborious lever, but it is hard to get that the middle point of force will move a considerable distance as long as it moves a short distance.
Both levers are useful, but it is necessary to evaluate whether it is necessary to save labor or range of motion. Archimedes, an ancient Greek scientist, famously said, "If you give me a fulcrum, I can pry up the earth", which is not only an inspiring aphorism, but also has a strict scientific basis.
References:
Baidu encyclopedia-lever principle