Teaching and research: Hooke s law, gravitational law, Coulomb s law, and so on

No, it's because the students accept it so much that they have no choice but to teach it like this.

Middle school is nothing more than summing up physical equations such as Newton's laws from experimental phenomena, because this is the ability of middle school students to accept.

The university directly starts from the principle of minimum action, the Hamiltonian equation and so on, and completely mathematics introduces the same results as Newtonian equations and other physical equations, which requires advanced mathematics and a higher mathematical foundation, so it is impossible to do this in secondary school.

But universities can do this, and they have to, take Newton's equation as an example, f=ma, right? Some people question, because these quantities were defined by Newton himself, how are they defined? It is defined by this equation, so how to calculate this equation will not be wrong, and there is a problem logically, the problem of circular definition.

In the microscopic realm, this equation is also powerless, for example, in quantum mechanics the example does not have fixed coordinates (according to the uncertainty relation), then acceleration (the second derivative of displacement versus time) does not exist. All this shows that Newtonian mechanics does not really reveal the essence of physical laws, what is essence? The principle of minimum action may be the basis for the collapse of analytical mechanics, but of course it is only possible, and it may be found that it needs to be corrected one day.

Of course, more essential things should be taught in universities.

As for the connection with middle school, I was also helpless along the way, did junior high school start with those equations that scared people to death? Then we must complete at least upper math in primary school. In fact, for many people, Newton's set is enough, even if the accuracy of the Newton's equations in the spacecraft should be enough, the relativity correction estimate can be ignored (I haven't calculated, so I use the estimate), as for the major involving physics in college, if you want to learn a little depth, start to understand physics again, and the middle school is just an inaccurate science popularization activity, so you don't have to worry about it.

Are you a teacher? How could the teacher say such a ridiculous thing?

Don't complain in China!!

To put it simply, it may be a coincidence in nature, but if you think about it, the coincidence is nothing more than saying that they are similar in form. The gravitational force is proportional to the product of the masses of two objects and inversely proportional to the square of the distance; The Coulomb force is directly proportional to the product of the charge at two points, and the square of the same distance is also inversely proportional. Both laws study the forces of two objects of similar nature to each other, and naturally, they must be related to both, so what is confusing is the inverse law of force and distance.

In Coulomb's law, the force between two point charges is due to a magnetic field of a certain strength generated around the point charge, and the force between them is essentially the action of the magnetic field force. So is gravitational force also an action of a magnetic field force? It seems hard to connect and hard to understand.

Because this does not seem to conform to the concept of magnetic field in the electromagnetic theory that we know, because the magnetic field we know is a concept with the negativity of ants. However, from the unity of nature and various phenomena, it is inferred that gravitational force should be the effect of a magnetic force. This magnetic field is intrinsic to the object, it is the inherent magnetism between all objects, and it is a non-polar attraction.

Only in this way can we fully and appropriately explain the phenomena related to the universe and nature.

This is precisely the connection between the electromagnetic force and the gravitational force, the macroscopic and the microscopic connection.

Coulomb's Law: It is one of the fundamental laws of electromagnetic field theory. The force between two stationary point charges in a vacuum is proportional to the product of the charge carried by these two charges, and inversely proportional to the square of their distance, and the direction of the force is along the line of the two point charges, and the charges of the same name repel each other, and the charges of the same name attract.

Formula: f=k*(q1*q2) r 2.

The law of gravitation: any two particles are attracted to each other by a force in the direction of a concentric line. The magnitude of this gravitational force is directly proportional to the product of their masses and inversely proportional to the square of their distance, independent of the chemical nature or physical state of the two objects and the intermediary matter.

The two are similar in form, but in fact, Coulomb's conclusion of Coulomb's law between charges is inspired by the basic formula of universal gravitation.

Coulomb's law states that electrons move in the direction of flow from the negative electrode to the positive electrode.

Hooke's Law.

Within the elastic limit, the elastic force of the spring is proportional to the deformation (elongation or compression value) of the spring. Writing:

f=k·x, where: "f", represents the elastic force of the spring, and the elastic force is the force applied to the force applied when the spring is deformed.

x" is the length of the spring elongation or shortening, note that "x" is based on the length of the spring when it is invisible, that is, x=x'-x0 or x=x0-x'.

k", called the stiffness coefficient of the spring, it describes the magnitude of the elastic force generated by the unit deformation, and the large k value indicates that the force required for the long deformation unit is large, or the spring is "hard".k is related to the spring material, length, thickness, etc. The SI unit of k is Nm.

If several identical springs are connected in series or parallel, the stiffness coefficient of the new spring is no longer the original stiffness factor. As shown in Fig. (1), if the stiffness coefficient of two springs with stiffness coefficients of k is k1 in series, then there is f=k1·x, and since the elastic force of point a is also f, the stiffness coefficient of two springs with the same original length k can be written for spring 1 when k2 is k2 when they are connected in parallel.

f=k2·x

Hooke's law is defined by RHooke proposed in 1678 that the expression is f=-k·x or f=-k·δx, where k is a constant, which is the stiffness coefficient (stubbornness coefficient) (elastic coefficient) of the object. In the International System of Units, the unit of f is the ox, the unit of x is the meter, which is the deformation (elastic deformation), and the unit of k is the number of bulls.

The stiffness coefficient is numerically equal to the elastic force of the spring when it is elongated (or shortened) per unit length.

Hooke's law of elasticity states that when a spring undergoes elastic deformation, the elastic force f of the spring is proportional to the elongation (or compression) x of the spring, that is, f = k·x. k is the coefficient of elasticity of a substance, which is determined only by the properties of the material and has nothing to do with other factors.

A negative sign indicates that the spring produces an elastic force in the opposite direction of its elongation (or compression).

The elastomer satisfies Hooke's law is an important physical theoretical model, which is a linear simplification of the complex nonlinear constitutive relations in the real world, and it has been proved to be effective to a certain extent. However, there are a large number of instances in reality that do not satisfy Hooke's law. Hooke's law is important not only because it describes the relationship between deformation and force in elastomers, but also because it opens up an important method of research

The linear simplification of complex nonlinear phenomena in the real world is not uncommon in theoretical physics.

1 And when he calculates the gravitational relationship between the planets, he assumes that the orbit of the planets is round. Is it okay to assume this?

That's to teach middle school students the assumptions that are easy to make in the textbook, and Newton deduced them from elliptical orbits.

2 Moreover, Newton merely proved that the gravitational pull between the apple and the planets is the same force. It is thought that gravity conforms to all objects in nature. Is there any basis for his conjecture?

There is no definite basis. Essentially, the law of gravitation is guessed. What Newton did was to prove that the gravitational pull between the Earth and the Moon is inversely proportional to the square and is the same force as gravity. Then guess that there is such a force in everything.

3. Does the descendants have any additional proof?

Yes, for example, in the most famous experiment of Cavendish to measure the gravitational constant, there is a gravitational force between any two lead balls. I only know the proof of gravity.

Newton's law of universal gravitation: f=gmm r 2, there is a gravitational force between objects, the magnitude is proportional to the product of the mass of the object, and inversely proportional to the square of the distance between objects, Newton's law of universal gravitation is a limit approximation of general relativity. Hooke's Law.

f=kx, k is the stiffness coefficient of an elastic object (spring), and x is the amount of change in the length of the object in the elastic range.

Newton's three laws can be found in the Principia Mathematica of Natural Philosophy

The gravitational constant is g = n·m 2 kg 2, Newton discovered the law of gravitation, but the value of the gravitational constant g is that the Englishman Cavendish used a torsion scale to skillfully measure this constant. Its experiment in determining the gravitational constant is also known as the experiment of measuring the weight of the earth.

There is no perfect theory yet, but there are conjectures in this area.