how to use leverage? When using a lever, in order to save labor, you should use a lever whose power arm is 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 lever can save labor and distance. However, if you want to save effort, you must move more distances; If you want to move less distance, you must work harder. It is impossible to save effort and move less distance. It is from these axioms that Archimedes discovered the lever principle on the basis of the "center of gravity" theory, that is, "when two weights are in balance, their distance from the fulcrum is inversely proportional to their weight.

When using a lever, in order to save labor, you should use a lever whose power arm is 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 lever can save labor and distance. However, if you want to save effort, you must move more distances; If you want to move less distance, you must work harder. It is impossible to save effort and move less distance. It is from these axioms that Archimedes discovered the lever principle on the basis of the "center of gravity" theory, that is, "when two weights are in balance, their distance from the fulcrum is inversely proportional to their weight. The fulcrum of the

lever at the entrance of Yonghua Securities doesn't have to be in the middle. A system that meets the following three points is basically a lever: fulcrum, force point and force point.

where the formula is written as follows: distance (moment) from fulcrum to stress point? *? Force? =? Distance from fulcrum to application point (arm of force)? *? Apply force, and this is a lever.

there are also labor-saving levers and laborious levers, both of which have different functions. For example, there is a kind of air pump with feet, or a juicer with hands, which is a labor-saving lever? (arm of force? > ? Torque); But we have to press down a long distance, and there is only a small movement at the stressed end. There is also a laborious lever. For example, a crane on the side of the road, the hook for fishing is at the tip of the whole pole, with the fulcrum at the end and the oil press in the middle? (torque? > ? Arm of force), this is a laborious lever, but what is gained by hard work is that the point of application in the middle will move a considerable distance as long as it moves a small distance.

both kinds of levers are useful, but where they are used, it is necessary to evaluate whether to save labor or range of motion. There is another thing called axle, which can also be used as a lever, but the performance may sometimes be added with the calculation of rotation.

Archimedes, an ancient Greek scientist, has such a famous saying: "If you give me a fulcrum, I can move the earth!" This sentence is not only an inspiring epigram, but also has a strict scientific basis.

lever classification

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levers can be divided into labor-saving levers, labor-saving levers and equal-arm levers. These types of levers have the following characteristics:

1. Labor-saving lever: L1 >; L2,? F1< F2? Save effort and distance. Such as claw hammer for pulling nails, hay cutter, bottle cap wrench, etc.

2. laborious lever:? L1＜L2,? F1 > F2, laborious and distance-saving, such as fishing rod and tweezers.

3. Equal arm lever:? L1＝L2,? F1 = F2, it is neither labor-saving nor laborious, and it does not move much. Levers are indispensable in almost every machine, even in the human body, there are many levers at work. Picking up a thing, bending down, or even tilting your toes are all the levers of the human body. Knowing the levers of the human body can not only increase physical knowledge, but also learn a lot of physiological knowledge.

Among them, most of them are laborious levers, and a small part are equal arm and labor-saving levers.

nodding your head or lifting your head depends on the action of the lever (see figure). The fulcrum of the lever is at the top of the spine, and there are muscles before and after the fulcrum. The weight of the head is resistance. The muscles before and after the fulcrum cooperate, and some contract and some lengthen to form a bow and head-up. From the picture, it can be seen that bowing is more labor-saving than looking up.

when the elbow lifts a heavy object, the arm is also a lever (pictured). The elbow joint is the fulcrum, and there are muscles on both sides of the fulcrum. This is a laborious lever. It takes more than 6 times of muscle strength to lift one weight. Although it is laborious, it can save a certain distance.

When you put your toes up, it is the muscles behind your heels that are at work, the toes are the fulcrum, and your weight falls in between. This is a labor-saving lever (pictured), and the muscle tension is smaller than the weight. And the longer the feet, the more labor-saving.

if you bend over, your muscles will exert a tension of nearly 12 newtons. This is? Because the lever formed between the waist muscles and the spine is also a laborious lever (pictured). ? So when bending down to lift a vertical object, the correct posture is to make the heavy object as close as possible to the body? Some. To avoid muscle strain.