In the sea area far away from Island 30 in the Chambord Islands, a group of young figures loomed on the sea, looking at the amusement park of Island 30 with a look of hope.

"The human world. ”

These young figures are not humans, but fishmen, who live on Fish-Man Island 10,000 meters below the Chambord Islands, this group of young fish-people has a variety of strange species, including sharks, goldfish, octopuses and so on.

"One day, I will build a paradise like that one, so that my people can live in the sun. Looking at the glittering amusement park gates, one of the shark people said with a determined expression.

"Brother Aaron, let's get out of here quickly, this is a place close to humans, and if they find out, they will definitely turn us into slaves. As he spoke, the goldfish man kept looking at the sea around him.

"What are you afraid of, what are the human beings who are comparable to us fishmen, in terms of strength and speed, they are comparable to us. The shark man exclaimed unpleasantly.

"Not good, there are humans there. At this moment, one of the fish-men pointed to a ship that had just appeared on the surface of the sea in the distance, and the next moment the figure of the fish-man disappeared from the sea.

Then the other fish-people immediately dived to the bottom of the sea, and only a young octopus man remained on the surface of the sea, looking at the amusement park with a pair of eyes intently.

"It's human. I don't know how long it took, just as the little octopus man was about to return to Fishman Island, he suddenly found a middle-aged man with blond hair floating not far away.

The little octopus man looked at the floating middle-aged man with a tangled face, and after a long time, the little octopus slowly approached the middle-aged man.

"Hey, it's alive. The little octopusman, who had thought that the man was dead, quickly moved away from the human after noticing that the man was still breathing weakly.

Later, after discovering that this human seemed to be unable to hurt him, the little octopus slowly approached the human again, and then slowly dragged the human to a nearby island, although the little octopus was still very young at this time, but he still knew the difference between a human and a fish man.

Humans are not like fish-people, they cannot stay in the sea for a long time.

"So it's here. Just as the little octopus man dragged the middle-aged blonde man to the shore, a dark-haired woman with a cigarette in her mouth appeared in front of them.

After seeing this woman, the little octopus man immediately prepared to jump into the sea, but unfortunately it was too late at this time, and before the little octopus could act, the black-haired woman had already appeared beside him and lifted him up with one hand.

"Good luck. The black-haired woman said as she held the middle-aged man on the ground in one hand and the small octopus in the other hand and walked towards the interior of the island.

The black-haired woman grabbed a large and a small two, and quickly came to the island where the thirteenth mangrove tree was located, and directly entered a stripper bar named Xia Qi.

"Looks like I shouldn't die, Xia Qi. After the first aid of the black-haired woman, the middle-aged blonde man finally woke up.

"For the World Government, you should be dead at this moment, Reilly. ”

"It's good news, it's finally time to have some dull days. ”

It was the Hades King Rayleigh who was rescued by the little octopus, and the battle with CP9 made him fall into the sea, if it weren't for the little octopus, maybe Rayleigh would really die.

Although afterwards, the World Government's spy organization did a lot of research in the Chambord Islands and found no trace of Reilly, over time, the World Government could only think that Reilly died under the pursuit of CP9, and both sides should have died together.

And Reilly happened to be able to live in seclusion in the Chambord Islands, and since then the Chambord Islands have a highly skilled coater Lao Lei.

When Reilly lived in seclusion in the Chambord Islands from then on, Night Mowgli was introduced by Tsuru to join the naval team trained by Admiral Zefa himself.

This is a team personally trained by Admiral Zefa, and countless navies hope to have this opportunity, and many of them are already in the upper echelons of the navy, hoping to arrange their own people in.

It's a pity that Zefa is notoriously unsentimental, he hopes to train the elite of the navy, not waste, and the navy recommended by the navy headquarters, branches, and the four seas branch has nearly 10,000 people.

However, the first level Zefa eliminated 9,000 of them, and only 1,000 people passed the first level, and the test of the first level was actually very simple, that is, the Dao power reached more than fifty.

Although the concept of Doli is not very useful in real combat, it still has some value in internal evaluation, like a dynamometer.

Of course, if you are a person with a Devil Fruit, even if your Dao power does not reach fifty, you can still pass the level.

Force is one of the fundamental concepts in mechanics and is the external cause that causes an object to gain acceleration or deformation. In dynamics, it is equal to the product of the mass of the object and the acceleration.

The concept of force forms a brief history of pushing and pulling objects, and one can intuitively become aware of the vague concept of "force". The movement of the object being pushed and pulled and the gradual slowing down of the object due to friction and finally stopping when the object slides reflect the action of the force. The ancient Chinese text "The Book of Ink" summarizes this concept as "force, the form of the cause of struggle." That is, force is what makes an object move. So, the force is naturally reflected in the consciousness of the person. But people have gone through a long struggle from intuitive awareness of the concept of "force" to obtaining a strict scientific definition of "force".

In the West, the concept of force was introduced before it was introduced in the physical sciences. First of all, there is a debate in philosophy. Thales and others of the cosmological school of ancient Greek wax believed that nature is alive, and like the human body, it is a living tissue that moves by itself. Under the guidance of this philosophical thought, there is no proposition of the origin of motion, and there is no concept of "force". Later, Parmnides came up with the idea that motion does not exist from logical reasoning. His opponents argue that the source of the movement is "force" to prove that the movement exists. This means acknowledging the original causal view that force is the cause and motion is the effect.

Plato's concept of force is essentially immaterial, and he believed that the nature of motion is given by nature solely because of an immortal living spirit. The final source of all forces in nature is the hidden soul of the world, which is the root of all physical activity. Of course, this metaphysical view is difficult to explain the kind of motion that gravity generates.

In the writings of Aristotle, force is seen as being emitted from one object to another. This emitted force is not matter in itself, but a "form" that exists in dependence on matter. According to this concept of force, its action is limited to objects that are in contact with each other; Aristotle's conception of force completely negates the existence of forces that act at a distance without touching each other. So we can only assume that the planets drive themselves into motion, and that the stars themselves are alive. But Aristotle was the first to come up with the so-called "law of motion", which states that the speed of a moving object is proportional to the resistance experienced as it passes through a medium. However, he did not propose the units of measurement to be used, nor did he have a method for measuring them. Aristotle believed that the weight of an object is a sign of "natural motion", i.e., a tendency of the object to return to its natural position, rather than a cause of the object's forced motion. This realization precludes the possibility of weight as a unit of measurement of force.

Throughout the Middle Ages, the concept of force was heavily bound by Aristotelian thought and did not make much progress.

Galileo made important contributions to the establishment of classical mechanics, but he did not form a complete concept of force. His definition of mass is vague, so he cannot give a clear definition of force that applies to both statics and dynamics. Of course, he has a basic understanding of the principle of inertia. His principle of inertia states that an object can move continuously at a uniform speed without being acted upon by an external force. He linked force to changes in velocity. It broke the long-standing shackles of Aristotle's idea of linking force and velocity, and opened the way for I. Newton to associate force and acceleration.

The concept of force occupies the most fundamental place in Newtonian mechanics. Newton proposed in 1664 that the definition of force is the temporal variability of momentum (momentum equals mass times velocity). Newton's first law (law of inertia) is a qualitative definition of force that gives qualitative conditions under what conditions a force exists and under what conditions it does not. Newton's second law gives a quantitative definition of force, i.e., force is equal to the temporal variability of momentum, and if the mass is constant, the force is also equal to the mass times the acceleration. Newton's third law states that for every force, there must be a reaction force of equal magnitude and opposite directions. It states that all forces are paired and can only be realized when two objects interact with each other (see Newton's laws of motion).

The astonishing achievement of Newton's theory of gravitation led to the extension of the concept of forces at great distances to other branches of physics. However, Newton could not physically explain the essence of the super-distance action, so it was severely criticized by all parties for a long time, and it was not until A. Einstein proposed the special theory of relativity in 1905, pointing out that the maximum speed of propagation of all physical actions is the speed of light, and people realized that Newton's concept of the over-distance action has great limitations. Albert Einstein made it clear in his general theory of relativity in 1915 that gravitational forces cannot travel faster than the speed of light.

Historically, many scientists and philosophers have pointed out that the concept of force in Newtonian mechanics is only a tool of methodological nature, and Kirchhoff, H.B. Hertz, and E. Mach all found Newton's concept of force difficult to explain the essence of force, but they all affirmed that force is a computational quantity, representing the product of mass and acceleration. Of course, Newton's concept of force has contributed greatly to the progress of science: without it, physics would lose its theoretical coherence.

Newton's second law, the unit of force, can be seen as both a definition of mass and a definition of force. The former sees force as a fundamental quantity and mass as a derived quantity of the second law, while the latter does the opposite.

We define a unit of length as the distance between two points of a standard scale, or measured in terms of a specific wavelength of spectral lines. Similarly, time can be used in the cycle of standard movement. It is measured by the orbital period of the earth, the oscillating period of a clock, or the vibrational period of a molecule. Using this unit of length and time, we can give definitions and measurements of velocity and acceleration. Now, let's explore Newton's second law in two ways, namely absolute and gravitational. In the absolute system, we introduce the mass of a standard object as a unit mass, so that according to the second law, the force per unit mass produces a unit acceleration as a unit force. In principle, the acceleration of other masses can be measured by the action of a unit force compared to a standard unit mass. The acceleration thus obtained is inversely proportional to its mass. It is empirically proven that mass is a scalar quantity, while force and acceleration are vector quantities, and they obey the laws of vector synthesis and decomposition.

In absolute, Newton's second law of non-relativistic mechanics can be written as:

f=ma，

where f and a are the forces and accelerations, and m is the mass of the object. If m and a on the right side of the equation are known, then this equation is the definition of force. So in the absolute system, mass is the basic quantity, and force is the derived quantity. The dimension of force is MLT-2, where m, l, and t are the dimensions of mass, length, and time, respectively.

In the gravitational system, the gravitational force of the earth on a standard object is used as the standard force, so the gravitational system takes the force as the fundamental quantity, and according to the second law, mass is the proportional factor of the force and the acceleration, which becomes the derived quantity. In the gravitational system, the weight of a standard object is taken as a unit force, and the gravitational acceleration is g. The weight of any object is measured in terms of the weight of a standard object. Let the weight of the object be , then its mass m can be written as /g. The dimension of this derived quantity m is ft2l-1, where f is the dimension of force. Since the gravitational acceleration of the Earth is not exactly equal everywhere on the Earth's surface, the weight of the object at all points on the Earth's surface is not exactly equal. In order to avoid this difficulty, a specific point on the earth's surface is prescribed as a place for measuring the standard weight of a standard object. Therefore, the absolute degree of gravitational system is no worse than the absolute degree of so-called absolute system.

The units of force in absolute are dyne and newton. 1 dyne is the force that causes a mass of 1 gram to produce an acceleration of 1 cm/s2, and 1 Newton is the force that causes a mass of 1 kilogram to produce an acceleration of 1 m/s2. 1 Newton is equal to 105 dynes. In the International System of Units and the Chinese legal unit of measurement, the unit of force is the newton.

Resultant forceIf the lines of action of all the forces intersect at one point, then these forces form a converging force system. The resultant force of any intersecting force system can be obtained by the vector summation method, but this resultant force must pass through the intersection point of the force system. If the resultant force is equal to zero, the converging force system is equilibrium, i.e., the object on which they act has no acceleration.

Generally speaking, there can be three types of forces acting on any larger object: 1. There are external forces acting on the area of some points or surfaces that are dispersed. 2 Inside the object, there is the action of the reaction force generated by the external force, or the action of the internal binding force due to the deformation of the object. These internal deformation constraints are generated in pairs, and together they cancel each other out and do not affect the acceleration. 3. It has the effect of distributing force in each part of the interior. These forces are generally proportional to the mass of the parts. For example, the force generated by weight and the inertial force caused by acceleration are both forces distributed in the body, which are collectively referred to as thorough physical strength, or physical strength for short. If the external forces on the object are converging, the resultant force must be equal to the physical force and in the opposite direction. If this resultant force passes through the center of mass of the object, then the resultant force must be equal to the total mass multiplied by the acceleration produced by the object. If the resultant force of these converging external forces does not pass through the center of mass of the object, this resultant force can be reduced to the sum of a force acting on the center of mass and a couple moment around the center of mass (see Force System). The magnitude and direction of the line of action of the former are the same as the original resultant force, except that the line of action translates to the position passing through the center of mass of the object, and the latter is equal to the vertical distance of the resultant force multiplied by the center of mass to the original line of action of the resultant;