The lever principle was invented by Archimedes. Archimedes has a long-standing famous saying: Give me a fulcrum and I can pry up the whole earth! This sentence is about the principle of leverage. In fact, as early as Archimedes more than 200 years ago, Mozi had a profound interpretation of the principle of lever balance. He called resistance "weight", resistance arm "base", force application "right" and force application arm "standard".

Mohist classics say: "Balance must be right, it is said that it will be won", "Balance, if aggravated, will be beaten. If the weight and weight are similar and balanced, the standard length will be short. If you add two things, the weight is similar, then the bid is next, and the bid is right. " It means that if the two sides are balanced, the lever must be horizontal, and if the weight of one side is increased, this side will inevitably sag.

Brief introduction of lever principle

The lever principle is also called "lever balance condition". In order to balance the lever, the two moments (product of force and arm) acting on the lever must be equal.

That is, power× power arm = resistance× resistance arm, which is expressed by algebraic expression as F 1 L 1 = F2 L2. Where F 1 stands for power, L 1 stands for power arm, F2 stands for resistance, and L2 stands for resistance arm. As can be seen from the above formula, to balance the lever, the power arm is several times that of the resistance arm, and the resistance is several times that of the power.

The principle of lever tells us that when using lever, in order to save labor, we should use lever with power arm longer than resistance arm; If you want to save distance, you should use a lever with a force arm shorter than a resistance arm.