Balance fulcrum, also known as lever balance condition, is a theorem to analyze the balance of lever force, which was first put forward by Archimedes, an ancient Greek scientist.

To achieve force balance, the product of the two moments acting on the lever and the arm must be equal in magnitude and opposite in rotation direction, that is to say, the balance condition of the lever must be met. The mathematical expression is F 1 L 1 = F2 L2, where F 1 stands for power and L65438.

Archimedes, an ancient Greek scientist, first put forward the lever principle in his book On the Balance of Plane Figures. He once famously said that if you give me a fulcrum, I can pry up the whole earth. This is the principle of leverage.

Before the lever principle was put forward, Archimedes regarded some empirical knowledge in lever practice as self-evident axioms. These axioms include: hanging equal weights at both ends of a weightless bar at the same distance from the fulcrum, they will be balanced; Weights with unequal weights are hung at both ends of the weightless bar with equal distance from the fulcrum, and weights with equal weight are hung at both ends of the weightless bar with unequal distance from the fulcrum, and the far ends are inclined downward.

The function of one weight can be replaced by the function of several evenly distributed weights, as long as the position of the center of gravity remains unchanged. On the contrary, several evenly distributed weights can be replaced by one weight hanging on their centers of gravity, and the centers of gravity of similar figures are distributed in a similar way.