I have learned in the human physiology and hygiene class that there are 206 bones in the human body, many of which act as levers. Of course, these lever bones cannot automatically rotate around the fulcrum and must be driven. The power comes from the muscles attached to it.

Muscles are attached to bones by tough tendons. For example, the upper tendon of the biceps brachii attaches to the scapula, the lower end of the tendon attaches to the radius, the upper end of the triceps brachii has tendons that attach to the scapula and humerus, and the lower end attaches to the ulna.

It is easiest to see the lever effect of bones in the movements of the human forearm, its fulcrum is at the elbow joint. When the biceps contract and the triceps relax, the forearm turns upward, causing the elbow to bend; when the triceps contracts and the biceps relax, the forearm turns downward, causing the elbow to extend. The forearm is a laborious lever, but just a little shortening of the peptide biceps allows the hand to move a considerable distance. It can be seen that it takes a lot of effort, but saves distance.

In the human body, bones rotate around the joint axis under the action of muscle tension. Its function is the same as a lever and is called a bone lever. There are three forms of bone lever movement in the human body:

(1) Balance lever: the fulcrum is between the force action point and the gravity action point. Such as head-up and head-down movements performed by the skull.

(2) Labor-saving lever: The gravity action point is between the fulcrum and the force action point. Such leverage can overcome greater body weight, such as the action of lifting your heel while walking.

(3) Speed ??lever: The action point of the force is between the gravity action point and the fulcrum. For example, the movement of the elbow joint requires a large force to overcome a small gravity, but the speed and range of movement are very large. Knowledge point: The principle of leverage

The ancient Greek scientist Archimedes has a famous saying that has been passed down through the ages: "Give me a fulcrum and I can lift the entire earth!" This sentence has a strict scientific basis. That is the principle of leverage. A hard rod that can rotate around a fixed point under the action of force is called a lever. In life, the lever can be made straight or curved according to needs, but it must be a hard rod.

Archimedes first proposed the lever principle in his book "On the Balance of Plane Figures". He first regarded some empirical knowledge in the practical application of levers as "self-evident axioms", and then based on these axioms, using geometry and rigorous logical argumentation, he derived the lever principle, that is, "when two heavy objects are balanced, Their distance from the fulcrum is inversely proportional to their weight. "Archimedes' research on levers was not just theoretical, but he also made a series of inventions based on this principle.