A deep understanding of the physical concept of work, the physical meaning of work

If you choose the sun as a reference, then both the apple and the earth will have a displacement (if only these two objects are considered), but the displacement of the earth is too small. Essentially, the apple and the earth are attracted to each other, and it is a gravitational force. The increase in the kinetic energy of the apple is due to the decrease in the potential energy of the system between the apple and the earth.

It's just that the mass of the earth is several orders of magnitude larger than that of apples, so the changes in the earth are not obvious.

Hehe, you have a good spirit of getting to the bottom of things! High school? Keep up the good work, and you will succeed!

To understand this concept, we can't take out the kinetic energy one-sidedly, but should understand it in the framework of mechanical energy, which is not a negative work, but just a simple transformation of energy, because the gravitational potential energy of the apple becomes smaller in the process of falling, and it is converted into the kinetic energy of the apple, which is the reason for the increase of kinetic energy. And the total mechanical energy of apples is constant. A kind of work that can not be created out of thin air cannot disappear out of thin air, and it is impossible to do the so-called negative work.

The negative work done by the apple to the outside world is the positive work done by the outside world to the apple, and this force is gravity.

It's a problem with your train of thought.

For example, if A does positive work on B and B's kinetic energy increases, does B necessarily do negative work on A? Of course, not necessarily, for example, two astronauts in space push each other and float away, obviously both of them are doing positive work on each other.

Why does Apple's kinetic energy increase? Of course, because other objects have some kind of effect on the apple, and considering the external effect of the apple cannot be answered correctly.

Also, to correct it, gravity does a positive job for apples here.

The kinetic energy increases and the potential energy decreases.

I would like to ask mama8008

Is the energy of the apple on the ground only kinetic energy?

Work is a measure of the transformation of energy.

Work is the process by which energy is transformed from one form to another. There are two necessary factors for work to be done: the force acting on the object and the distance the object passes in the direction of the force.

Definition of classical mechanics: When a force acts on an object and causes the object to pass a distance in the direction of the force, it is said in mechanics that the force has done work on the object.

Gong (English: work), also called mechanical work. If an object is subjected to a force and there is a displacement in the direction of the force, we are said to have done work on the object.

Work is a physical quantity in physics that represents the accumulation of force to displacement. Similar to mechanical energy, work is also a scalar quantity, and the SI unit is joules.

Work is the way to achieve energy transformation, or in other words, work is a sufficient and necessary condition for energy transformation.

If you don't do work, there will be no transformation of energy; When work is done, it must be accompanied by the transformation of energy. The process of doing work itself is the process of energy transformation, and the process of energy transformation itself is the process of doing work, and the two are like the positive and negative sides of a coin--- and work and energy conversion are inseparable.

The value of the work done is equal to the energy transformed, that is, the work is a measure of the energy transformation.

In many cases, it is difficult or even impossible to measure how much energy an object has and how much energy it converts, but the work that leads to the energy conversion can be measured, and we can know how much energy is converted by measuring the work.

The last point: there are positive and negative points of work, and the positive and negative of work determines (reflects) the direction of energy transformation. For example:

Gravity does positive work--- gravitational potential energy is converted into kinetic energy;

Gravity does negative work--- kinetic energy is converted into gravitational potential energy.

The product of the force and the distance that the object passes in the direction of the force is a physically significant quantity, and in physics this product is called mechanical work, or work for short.

Necessary conditions for doing work on an object:

The first is to have a strong effect on the object.

The second is that the object has to pass a certain distance in the direction of action of the force.

In the International System of Units, the unit of strength is the ox, and the unit of distance is the meter, and the unit of work is the ox per meter. In physics, there is a specialized name for joules, which is simply coke.

The definition and physical meaning of work are as follows:

Definition: Work, also called mechanical work, is a physical quantity in physics that represents the accumulation of space where a force acts on an object, work is a scalar quantity, and the magnitude is equal to the product of the distance between the force and the distance passed by the object in the direction of the force, and the SI unit is joules. The term "work" was first coined by the French mathematician Gustave Coriolli.

If an object is subjected to a force and there is a displacement in the direction of the force, we say that the force has done work on the object. The utility is represented by "w", and its formula is w=fscos. Its SI unit is joules, or coke for short, and is denoted by the letter "j".

Physical significance: The product of the distance between the force and the distance passed by the object in the direction of the force is a quantity with physical significance, and this product is called mechanical work in physics, referred to as work.

Work is a measure of the transformation of energy. Work is the process by which energy is transformed from one form to another. There are two essential factors that must be taken to do work: the force acting on the object and the distance the object passes in the direction of the force.

Supplementary information: Necessary conditions for doing work on an object:

The first is to have a strong role in the object.

The second is that the object has to pass a certain distance in the direction of action of the force.

In the International System of Units the unit of force is the ox, the unit of distance is the meter, and the unit of work is the ox per meter. In physics, there is a specialized name for joules, which is simply coke.

Work, also called mechanical work, is a physical quantity in physics that represents the accumulation of space where a force acts on an object, and work is a scalar quantity equal to the product of the force and the distance that the object passes in the direction of the force, and the SI unit is joules. The term "work" was first coined by the French mathematician Gustave Coriolli.

If a force acts on an object and the object moves some distance in the direction of this force, it is said in mechanics that the force has done work. Even if there is force, no work may be done. For example, in a uniform circular motion, the centripetal force does not do work because there is no change in the kinetic energy of the object doing circular motion.

In the same way, a book on the table, although the table is supportive of the book, does not do work because it is not displaced.

In general, there are three types of non-work: no work, no work, and vertical work. (No hard work:

Only the distance is moved, but no force is generated in the direction of this movement, i.e., 0·fs·cos = 0 joules; There is no work: there is only force, but there is no movement of a certain distance in the direction of the force, f·0·scos = 0 joules; Vertical reactive power: the object is both subjected to force and passes through a certain distance, but the two directions are perpendicular to each other, fscos90°=fs·0=0j.

> work is defined as the inner product of force and displacement. where w denotes work, f denotes force, and dx denotes a small displacement in the same direction as an external force; The above equation should be expressed as path integral, where a is the starting point of the integrated path and b is the end point of the integrated path. The concept of work is defined in order to understand the effect of an object acting on a force over a certain distance.

Work is a scalar quantity, so the positive and negative aspects of work do not indicate direction. The positive or negative of the work does not indicate the magnitude of the work. It simply indicates whether the dynamic force does the work on the object or the drag force does the work on the object, or whether the force does the work on the object or the object overcomes this force.

If you want to compare the amount of work done, you should compare the absolute value of the work, the work done by the large absolute value is more, and the work done by the absolute value is small. Work is a measure of energy change, the amount of work done reflects the amount of energy change, and the positive and negative work reflects the direction of energy transformation (note: not the direction of space).

1. Work refers to the distance that the object has moved in the direction of the pulling force, if it has applied force to the object, but there is no moving distance, then there is no work done, if the distance to the object is moved but there is no force, and there is no work, for example, a bullet sent out from the muzzle of the gun, it is only subject to gravity, so there is no work. w has = g object h, w total = f*s, are two formulas.

2. Introduction to Physics: Physics is a discipline that studies the most general laws of the motion of matter and the basic structure of matter. As a leading discipline in the natural sciences, physics studies the most basic forms and laws of motion of all matter, from the universe to elementary particles, and thus becomes the research foundation of other natural science disciplines.