See what “Weight” is in other dictionaries. Weight force, formulas What is body weight how to find it

Today we will raise a seemingly insignificant, but in fact very important topic. Namely, we will look at the difference between mass and weight. A school graduate knows that weight and mass are not the same thing. But even the most titled physicist will not tell the seller: “Give me a kilogram of apples.” He will say “weigh”, meaning the amount of apple product, not its heaviness. Let us reveal the mystery of this state of affairs.

Let's look through the physics textbook

Weight is a force, a variable quantity, measured in Newtons, meaning the effect on the support of a lying object or the tension of a suspension. Mass is the amount of substance inside the body, calculated in kilograms, tons, pounds, etc., and is a constant value.

For stationary objects, the values of these parameters are directly proportional. When weighing, the force with which the product presses on the stand is determined, and the display shows its mass. Very convenient for sellers and buyers.

When does difference occur?

The farther from the center of the Earth, the smaller the g, and the lighter the body.
Inertia. When an airplane or rocket takes off, the pilot experiences overload. The inertia of the start was added to its gravity, and the pressure on the support (chair) increased. On the contrary, when the elevator moves down, the passenger becomes lighter and puts less pressure on the floor.
A falling object weighs nothing, since K = g - g = 0. This is a state of weightlessness, although the mass remains the same.
Under the conditions of other planets, gravity changes. On the Moon g=1.62, and on Mars 3.86. The same body on the Moon is 6 times lighter, on Mars - 2.5 times lighter than under terrestrial conditions.

Why does confusion happen?

A person perceives the world through sensations. We cannot feel mass, but we can feel weight. The girl is holding a book. In this case, the palm is a support. The book presses, the hand resists. The reader feels the effort to hold the book. Reaction is the only way of determining mass given to us by nature. Hence the reason for the substitution of concepts, the discrepancy between the norms of language and physical phenomena.

In everyday life, the concepts of “mass” and “weight” are absolutely identical, although their semantic meaning is fundamentally different. Asking "What's your weight?" we mean "How many kilograms are you?" However, to the question with which we are trying to find out this fact, the answer is given not in kilograms, but in newtons. I'll have to go back to school physics.

Body weight- a quantity characterizing the force with which the body exerts pressure on the support or suspension.

For comparison, body mass previously roughly defined as "amount of substance", the modern definition is:

Weight - a physical quantity that reflects a body’s ability to inertia and is a measure of its gravitational properties.

The concept of mass in general is somewhat broader than that presented here, but our task is somewhat different. It is quite enough to understand the fact of the real difference between mass and weight.

In addition, they are kilograms, and weights (as a type of force) are newtons.

And, perhaps, the most important difference between weight and mass is contained in the weight formula itself, which looks like this:

where P is the actual weight of the body (in Newtons), m is its mass in kilograms, and g is the acceleration, which is usually expressed as 9.8 N/kg.

In other words, the weight formula can be understood using this example:

Weight mass 1 kg is suspended from a stationary dynamometer in order to determine its weight. Since the body, and the dynamometer itself, are at rest, we can safely multiply its mass by the acceleration of free fall. We have: 1 (kg) x 9.8 (N/kg) = 9.8 N. It is with this force that the weight acts on the dynamometer suspension. From this it is clear that the body weight is equal to However, this is not always the case.

It's time to make an important point. The weight formula equals gravity only in cases where:

the body is at rest;
the Archimedes force (buoyant force) does not act on the body. An interesting fact is that a body immersed in water displaces a volume of water equal to its weight. But it doesn’t just push out water; the body becomes “lighter” by the volume of displaced water. That’s why you can lift a girl weighing 60 kg in water by joking and laughing, but on the surface it is much more difficult to do.

When the body moves unevenly, i.e. when the body and the suspension move with acceleration a, changes its appearance and weight formula. The physics of the phenomenon changes slightly, but in the formula such changes are reflected as follows:

P=m(g-a).

As can be replaced by the formula, the weight can be negative, but for this the acceleration with which the body moves must be greater than the acceleration of gravity. And here again it is important to distinguish weight from mass: negative weight does not affect mass (the properties of the body remain the same), but it actually becomes directed in the opposite direction.

A good example is with an accelerated elevator: when it accelerates sharply, it creates the impression of being “pulled towards the ceiling” for a short time. It is, of course, quite easy to encounter such a feeling. It is much more difficult to experience the state of weightlessness, which is fully felt by astronauts in orbit.

Zero gravity - essentially a lack of weight. In order for this to be possible, the acceleration with which the body moves must be equal to the notorious acceleration g (9.8 N/kg). The easiest way to achieve this effect is in low-Earth orbit. Gravity, i.e. attraction still acts on the body (satellite), but it is negligible. And the acceleration of a satellite drifting in orbit also tends to zero. This is where the effect of the absence of weight arises, since the body does not come into contact with either the support or the suspension, but simply floats in the air.

Partially this effect can be encountered when an airplane takes off. For a second there is a feeling of being suspended in the air: at this moment the acceleration with which the plane is moving is equal to the acceleration of gravity.

Returning to the differences again weight And masses, It is important to remember that the formula for body weight is different from the formula for mass, which looks like :

m= ρ/V,

that is, the density of a substance divided by its volume.

Weight P of a body at rest in an inertial frame of reference, coincides with the force of gravity acting on the body, and is proportional to the mass and acceleration of gravity at a given point:

The weight value (with a constant body mass) is proportional to the acceleration of gravity, which depends on the height above the Earth’s surface (or the surface of another planet, if the body is located near it, not the Earth, and the mass and size of this planet), and, due to the non-sphericity of the Earth, and also due to its rotation (see below), from the geographic coordinates of the measurement point. Another factor influencing the acceleration of gravity and, accordingly, the weight of a body are gravitational anomalies caused by the structural features of the earth's surface and subsoil in the vicinity of the measurement point.

When the system moves, the body - support (or suspension) relative to the inertial reference frame with acceleration, the weight ceases to coincide with the force of gravity:

However, a strict distinction between the concepts of weight and mass is accepted mainly in physics, and in many everyday situations the word “weight” continues to be used when in fact we are talking about “mass”. For example, we say that an object "weighs one kilogram" even though a kilogram is a unit of mass. In addition, the term “weight” in the meaning of “mass” is traditionally used in the cycle of human sciences - in the combination “weight of the human body”.

Notes

Noun, m., used. often Morphology: (no) what? weight and weight, what? weight, (see) what? weight of what? weight, about what? about weight; pl. What? weight, (no) what? scales, why? scales, (see) what? weight, what? scales, about what? about scales 1. The weight of any physical... ... Dmitriev's Explanatory Dictionary

A(y); m. 1. Phys. Gravity. 2. Unwind and special Quantity, mass of someone or something, determined by weighing. V. goods, luggage. Lightweight and heavyweight wrestler. A container weighing one hundred kilograms. Gain, lose weight. Gain, lose weight... ... encyclopedic Dictionary

WEIGHT, weights (y), pl. weight (special), male 1. The gravity of a body towards the ground, the pressure of a body on some surface (physical). 2. The heaviness of the body expressed in numerical terms (determined using scales). Determine weight. A bag weighing 5 kg. How much is there... Ushakov's Explanatory Dictionary

See authority, importance, dignity, worth its weight in gold, with weight... Dictionary of Russian synonyms and similar expressions. under. ed. N. Abramova, M.: Russian Dictionaries, 1999. weight mass; authority, prestige, authority, influence, ... ... Synonym dictionary

WEIGHT, the force of GRAVITATIONAL attraction of a body. The weight of a body is equal to the product of the mass of the body and the acceleration of gravity. The mass remains constant, but the weight depends on the location of the object on the Earth's surface. As height increases, weight decreases... Scientific and technical encyclopedic dictionary

The quantity of goods supplied or offered for delivery. There is also a distinction between shipping weight, indicated in the transportation documents, and unloaded weight, indicated in the weight verification report. Dictionary of business terms. Akademik.ru. 2001... Dictionary of business terms

weight- WEIGHT, ah, m. Iron. Significance, dignity of someone or something. You are now the boss, you now weigh like a pregnant elephant. You don’t kill me with your weight. Maintain weight and behave pompously, with excessive importance, with emphasized dignity. From high… … Dictionary of Russian argot

WEIGHT, the force with which a body acts on a horizontal support (or suspension) that prevents it from free fall. If the support (suspension) is at rest or moves uniformly and rectilinearly, the weight is numerically equal to the product of the body mass by... ... Modern encyclopedia

The force with which a body acts on a horizontal support (or suspension) that prevents it from falling freely. Numerically equal to the product of the body mass and the acceleration of gravity. Due to the nonsphericity of the Earth and its daily rotation, the weight of this body... Big Encyclopedic Dictionary

Books

Funny hide-and-seek games. On vacation. Funny hide-and-seek games. In the knight's castle, Merry hiding places: on vacation. Brother and sister Tim and Anne went to the sea with their parents on vacation. Together with them you will go to the airport, ride a boat and explore... Category:

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Attention! Slide previews are for informational purposes only and may not represent all the features of the presentation. If you are interested in this work, please download the full version.

This presentation is intended to help students in grades 9-10 when preparing the topic “Body weight”.

Presentation objectives:

Repeat and deepen the concepts: “gravity”; "body weight"; "weightlessness".
Focus students' attention on the fact that gravity and body weight are different forces.
Teach students to determine the weight of a body moving vertically.

In everyday life, body weight is determined by weighing. From the 7th grade physics course we know that gravity is directly proportional to the mass of a body. Therefore, the weight of a body is often identified with its mass or gravity. From a physics point of view, this is a gross mistake. Body weight is a force, but gravity and body weight are different forces.

Gravity is a special case of the manifestation of the forces of universal gravity. Therefore, it is appropriate to recall the law of universal gravitation, as well as the fact that the forces of gravitational attraction manifest themselves when bodies or one of the bodies have enormous masses (slide 2).

When applying the law of universal gravitation for terrestrial conditions (slide 3), the planet can be considered as a homogeneous ball, and small bodies near its surface as point masses. The radius of the earth is 6400 km. The mass of the Earth is 6∙10 24 kg.

= ,
where g is the acceleration of free fall.

Near the Earth's surface g = 9.8 m/s 2 ≈ 10 m/s 2.

Body weight is the force with which this body acts on a horizontal support or stretches a suspension.

Fig.1

In Fig. Figure 1 shows a body on a support. The support reaction force N (F control) is applied not to the support, but to the body located on it. The modulus of the ground reaction force is equal to the modulus of weight according to Newton's third law. Body weight is a special case of the manifestation of elasticity. The most important feature of weight is that its value depends on the acceleration with which the support or suspension moves. Weight is equal to gravity only for a body at rest (or a body moving at constant speed). If the body moves with acceleration, then the weight can be greater or less than the force of gravity, and even equal to zero.

The presentation, using the example of solving Problem 1, examines various cases of determining the weight of a load weighing 500 g suspended from a dynamometer spring, depending on the nature of the movement:

a) the load is lifted upward with an acceleration of 2 m/s 2 ;
b) the load is lowered down with an acceleration of 2 m/s 2 ;
c) the load is evenly lifted up;
d) the weight falls freely.

Tasks for calculating body weight are included in the “Dynamics” section. The solution of dynamics problems is based on the use of Newton's laws with subsequent projection onto selected coordinate axes. This determines the sequence of actions.

A drawing is made showing the forces acting on the body(s) and the direction of acceleration. If the direction of acceleration is unknown, it is chosen arbitrarily, and solving the problem gives an answer about the correctness of the choice.
Write Newton's second law in vector form.
Select axes. Typically, it is convenient to direct one of the axes along the direction of acceleration of the body, and the second - perpendicular to the acceleration. The choice of axes is determined by considerations of convenience: so that the expressions for the projections of Newton's laws would have the simplest form.
The vector equations obtained in projections on the axes are supplemented with relations arising from the text of the problem conditions. For example, equations of kinematic relations, definitions of physical quantities, Newton's third law.
Using the resulting system of equations, they try to answer the question of the problem.

Setting up animation in a presentation allows you to emphasize the sequence of actions when solving problems. This is important, since the skills acquired by solving problems to calculate body weight will be useful to students when studying other topics and sections of physics.

Solution to problem 1.

1a. The body moves with an acceleration of 2 m/s 2 upward (slide 7).

Fig.2

1b. The body moves with acceleration downwards (slide 8). We direct the OY axis downward, then the projections of gravity and elasticity in equation (2) change signs, and it looks like:

(2) mg – F control = ma.

Therefore, P = m(g-a) = 0.5 kg∙(10 m/s 2 - 2 m/s 2) = 4 N.

1st century With uniform motion (slide 9), equation (2) has the form:

(2) mg – F control = 0, because there is no acceleration.

Therefore, P = mg = 5 N.

1 year In free fall = (slide 10). Let's use the result of solving problem 1b:

P = m(g – a) = 0.5 kg(10 m/s 2 – 10 m/s 2) = 0 H.

The state in which the body weight is zero is called the state of weightlessness.

The body is only affected by gravity.

Speaking about weightlessness, it should be noted that astronauts experience a prolonged state of weightlessness during flight with the spacecraft engines turned off.

ship, and to experience a short-term state of weightlessness, you just need to jump. A running person at the moment when his feet do not touch the ground is also in a state of weightlessness.

The presentation can be used in class to explain the topic “Body weight”. Depending on the level of preparation of the class, students may not be offered all the slides with solutions to problem 1. For example, in classes with increased motivation to study physics, it is enough to explain how to calculate the weight of a body moving with upward acceleration (task 1a), and the remaining problems (b , c, d) provide for independent decision with subsequent verification. Students should try to draw conclusions obtained as a result of solving problem 1 on their own.

Conclusions (slide 11).

Body weight and gravity are different forces. They have different natures. These forces are applied to different bodies: gravity - to the body; body weight - to the support (suspension).
The weight of a body coincides with the force of gravity only when the body is stationary or moves uniformly and rectilinearly, and other forces, except gravity and reaction of the support (suspension tension), do not act on it.
The weight of a body is greater than the force of gravity (P > mg) if the acceleration of the body is directed in the direction opposite to the direction of gravity.
Body weight is less than gravity (P< mg), если ускорение тела совпадает по направлению с силой тяжести.
The state in which the body weight is zero is called the state of weightlessness. A body is in a state of weightlessness when it moves with the acceleration of gravity, that is, when only the force of gravity acts on it.

Tasks 2 and 3 (slide 12) can be offered to students as homework.

The presentation “Body Weight” can be used for distance learning. In this case it is recommended:

when viewing the presentation, write down the solution to problem 1 in your notebook;
independently solve problems 2, 3, using the sequence of actions proposed in the presentation.

A presentation on the topic “Body weight” allows you to show the theory of solving problems on dynamics in an interesting, accessible interpretation. The presentation activates the cognitive activity of students and allows them to form the correct approach to solving physical problems.

Literature:

Grinchenko B.I. Physics 10-11. Problem solving theory. For high school students and those entering universities. – Velikiye Luki: Velikiye Luki City Printing House, 2005.
Gendenshtein L.E. Physics. Grade 10. At 2 o'clock Ch 1./L.E. Gendenshtein, Yu.I. Dick. – M.: Mnemosyne, 2009.
Gendenshtein L.E. Physics. Grade 10. At 2 p.m. Part 2. Problem book./L.E. Gendenshtein, L.A. Kirik, I.M. Gelgafgat, I.Yu. Nenashev. - M.: Mnemosyne, 2009.

Internet resources:

images.yandex.ru
videocat.chat.ru

Quite a lot of mistakes and non-random slips by students are related to the strength of the weight. The phrase “power of weight” itself is not very familiar, because We (teachers, authors of textbooks and problem books, teaching aids and reference books) are more accustomed to saying and writing “body weight”. Thus, the phrase itself takes us away from the concept that weight is force, and leads to the fact that body weight is confused with body weight (in the store we often hear people asking to weigh several kilograms of a product). The second common mistake students make is confusing the force of weight with the force of gravity. Let's try to understand the force of weight at the level of a school textbook.

First, let's look at the reference literature and try to understand the authors' point of view on this issue. Yavorsky B.M., Detlaf A.A. (1) in the reference book for engineers and students, the weight of a body is the force with which this body acts due to gravity towards the Earth on the support (or suspension) that holds the body from free fall. If the body and the support are motionless relative to the Earth, then the weight of the body is equal to its gravity. Let's ask a few naive questions about the definition:

1. What reporting system are we talking about?

2. Is there one support (or suspension) or several (supports and suspensions)?

3. If a body gravitates not towards the Earth, but, for example, towards the Sun, will it have weight?

4. If a body in a spaceship moving with acceleration “almost” does not gravitate toward anything in observable space, will it have weight?

5. How is the support located relative to the horizon, is the suspension vertical for the case of equality of body weight and gravity?

6. If a body moves uniformly and rectilinearly along with a support relative to the Earth, then the weight of the body is equal to its gravity?

In the reference guide to physics for those entering universities and self-education by B.M. Yavorsky. and Selezneva Yu.A. (2) give an explanation of the last naive question, leaving the first ones unattended.

Koshkin N.I. and Shirkevich M.G. (3) it is proposed to consider the body weight as a vector physical quantity, which can be found using the formula:

The examples below will show that this formula works in cases where no other forces act on the body.

Kuhling H. (4) does not introduce the concept of weight as such at all, identifying it practically with the force of gravity; in the drawings the weight force is applied to the body, and not to the support.

In the popular “Physics Tutor” by I.L. Kasatkina. (5) the weight of a body is defined as the force with which the body acts on a support or suspension due to attraction to the planet. In the following explanations and examples given by the author, answers are given only to the 3rd and 6th of the naive questions.

Most physics textbooks give definitions of weight that are more or less similar to the definitions of the authors (1), (2), (5). When studying physics in the 7th and 9th grades, this may be justified. In 10th specialized classes with such a definition, when solving a whole class of problems, one cannot avoid various kinds of naive questions (in general, there is no need to strive to avoid any questions at all).

Authors Kamenetsky S.E., Orekhov V.P. in (6) distinguishing and explaining the concepts of gravity and body weight, they write that body weight is a force that acts on a support or suspension. That's all. There is no need to read between the lines. True, I still want to ask, how many supports and suspensions, and can a body have both support and suspension at once?

And finally, let's look at the definition of body weight given by V.A. Kasyanov. (7) in the 10th grade physics textbook: “the weight of a body is the total elastic force of the body, acting in the presence of gravity on all connections (supports, suspensions).” If we remember that the force of gravity is equal to the resultant of two forces: the force of gravitational attraction to the planet and the centrifugal force of inertia, provided that this planet rotates around its axis, or some other inertial force associated with the accelerated movement of this planet, then One could agree with this definition. Since no one is stopping us from imagining a situation where one of the components of gravity will be negligible, for example, the case of a spaceship in deep space. And even with these reservations, it’s tempting to remove the mandatory presence of gravity from the definition, because situations are possible when there are other inertial forces not associated with the movement of the planet or Coulomb forces of interaction with other bodies, for example. Or agree with the introduction of a certain “equivalent” force of gravity in non-inertial reporting systems and give a definition of weight force for the case when there is no interaction of the body with other bodies, except for the body creating gravitational attraction, supports and suspensions.

And yet, let’s decide when the weight of a body is equal to the force of gravity in inertial reporting systems?

Let's assume we have one support or one suspension. Is it sufficient that the support or suspension is stationary relative to the Earth (we consider the Earth to be an inertial frame of reference), or that it moves uniformly and rectilinearly? Let's take a fixed support located at an angle to the horizontal. If the support is smooth, then the body slides along an inclined plane, i.e. does not rest on a support and is not in free fall. And if the support is rough enough that the body is at rest, then either the inclined plane is not a support, or the weight of the body is not equal to the force of gravity (you can, of course, go further and question that the weight of the body is not equal in magnitude and not opposite in direction ground reaction force, and then there will be nothing to talk about at all). If we consider the inclined plane to be a support, and the sentence in parentheses to be irony, then, solving the equation for Newton’s second law, which for this case will also be the condition for the equilibrium of a body on an inclined plane, written in projections onto the Y axis, we will obtain the expression for weight other than gravity:

So, in this case, it is not enough to say that the weight of a body is equal to the force of gravity when the body and the support are motionless relative to the Earth.

Let us give an example with a suspension and a body on it that are motionless relative to the Earth. A positively charged metal ball on a thread is placed in a uniform electric field so that the thread makes a certain angle with the vertical. Let us find the weight of the ball from the condition that the vector sum of all forces is equal to zero for a body at rest.

As we see, in the above cases, the weight of the body is not equal to the force of gravity when the condition of immobility of the support, suspension and body relative to the Earth is met. The peculiarities of the above cases are the existence of the friction force and the Coulomb force, respectively, the presence of which actually leads to the fact that the bodies are kept from moving. For vertical suspension and horizontal support, additional forces are not needed to keep the body from moving. Thus, to the condition of immobility of the support, suspension and body relative to the Earth, we could add that the support is horizontal and the suspension is vertical.

But would this addition solve our question? Indeed, in systems with vertical suspension and horizontal support, forces can act that reduce or increase the weight of the body. These could be the Archimedes force, for example, or the Coulomb force directed vertically. Let's summarize for one support or one suspension: the weight of a body is equal to the force of gravity when the body and the support (or suspension) are at rest (or uniformly and linearly moving) relative to the Earth, and only the reaction force of the support (or the elastic force of the suspension) and the force act on the body gravity. The absence of other forces, in turn, assumes that the support is horizontal and the suspension is vertical.

Let us consider cases when a body with several supports and/or suspensions is at rest (or moves uniformly and rectilinearly with them relative to the Earth) and no other forces act on it except the reaction forces of the support, the elastic forces of the suspensions, and attraction to the Earth. Using the definition of weight force by Kasyanov V.A. (7), we will find the total elastic force of the body connections in the first and second cases presented in the figures. Geometric sum of elastic forces of bonds F, in modulus equal to the weight of the body, based on the equilibrium condition, is really equal to the force of gravity and opposite to it in direction, and the angles of inclination of the planes to the horizon and the angles of deviation of the suspensions from the vertical do not affect the final result.

Let's consider an example (figure below), when in a system stationary relative to the Earth the body has a support and suspension and no other forces act in the system except the forces of elastic connections. The result is similar to the above. The weight of the body is equal to the force of gravity.

So, if a body is on several supports and (or) suspensions, and is at rest with them (or moves uniformly and rectilinearly) relative to the Earth, in the absence of other forces except gravity and the forces of elasticity of connections, its weight is equal to the force of gravity. In this case, the location of supports and hangers in space and their number do not affect the final result.

Let's consider examples of finding body weight in non-inertial reporting systems.

Example 1. Find the weight of a body of mass m moving in a spaceship with acceleration A in “empty” space (so far away from other massive bodies that their gravity can be neglected).

In this case, two forces act on the body: the inertial force and the support reaction force. If the acceleration in magnitude is equal to the acceleration of gravity on Earth, then the weight of the body will be equal to the force of gravity on Earth, and the bow of the ship will be perceived by astronauts as the ceiling, and the tail as the floor.

The artificial gravity created in this way for the astronauts inside the ship will be no different from the “real” earthly one.

In this example, we neglect the gravitational component of gravity due to its smallness. Then the force of inertia on the spaceship will be equal to the force of gravity. In view of this, we can agree that the cause of body weight in this case is gravity.

Let's return to Earth.

Example 2.

Relative to the ground with acceleration A A cart is moving, on which a body is attached to a thread of mass m, deflected at an angle from the vertical. Find the weight of the body, neglect air resistance.

The problem is with one suspension, therefore, the weight is equal in magnitude to the elastic force of the thread.

Thus, you can use any formula to calculate the elastic force, and, therefore, the weight of the body (if the air resistance force is sufficiently large, then it will need to be taken into account as a term to the inertia force).

Let's work with the formula some more

Therefore, by introducing the “equivalent” force of gravity, we can state that in this case the weight of the body is equal to the “equivalent” force of gravity. And finally we can give three formulas for its calculation:

Example 3.

Find the weight of a racing driver of mass m in a moving vehicle with acceleration A car.

At high accelerations, the reaction force of the seat back support becomes significant, and we will take it into account in this example. The total elastic force of the connections will be equal to the geometric sum of both support reaction forces, which in turn is equal in magnitude and opposite in direction to the vector sum of the forces of inertia and gravity. For this problem, we find the module of the weight force using the formulas:

The effective acceleration of gravity is found as in the previous problem.

Example 4.

A ball on a string of mass m is fixed on a platform rotating at a constant angular velocity ω at a distance r from its center. Find the weight of the ball.

Finding the body weight in non-inertial reporting systems in the given examples shows how well the formula for body weight proposed by the authors in (3) works. Let's complicate the situation a little in example 4. Let's assume that the ball is electrically charged, and the platform, together with its contents, is in a uniform vertical electric field. What is the weight of the ball? Depending on the direction of the Coulomb force, the weight of the body will decrease or increase:

It so happened that the question of weight naturally came down to the question of gravity. If we define the force of gravity as the resultant of the forces of gravitational attraction to a planet (or to any other massive object) and inertia, taking into account the principle of equivalence, leaving the origin of the force of inertia itself in the fog, then both components of gravity, or one of them, at least will cause body weight. If in the system, along with the force of gravitational attraction, the force of inertia and the forces of elastic connections, there are other interactions, then they can increase or decrease the weight of the body, leading to a state where the weight of the body becomes equal to zero. And these other interactions can cause weight gain in some cases. Let's charge a ball on a thin non-conducting thread in a spaceship moving uniformly and rectilinearly in distant “empty” space (we will neglect gravitational forces due to their smallness). Let's place the ball in an electric field, the thread will stretch, and weight will appear.

Summarizing what has been said, we conclude that the weight of a body is equal to the force of gravity (or the equivalent force of gravity) in any system where no other forces act on the body except the forces of gravity, inertia and elasticity of connections. Gravity or "equivalent" gravity is most often the cause of weight force. The force of weight and the force of gravity have different natures and are applied to different bodies.

Bibliography.

1. Yavorsky B.M., Detlaf A.A. Handbook of physics for engineers and university students, M., Nauka, 1974, 944 p.

2. Yavorsky B.M., Selezneva Yu.A. Physics Reference Guide for

entering universities and self-education., M., Nauka, 1984, 383 p.

3. Koshkin N.I., Shirkevich M.G. Handbook of elementary physics., M., Nauka, 1980, 208 p.

4. Kuhling H. Handbook of physics., M., Mir, 1983, 520 p.

5. Kasatkina I.L. Physics tutor. Theory. Mechanics. Molecular physics. Thermodynamics. Electromagnetism. Rostov-on-Don, Phoenix, 2003, 608 p.

6. Kamenetsky S.E., Orekhov V.P. Methods for solving problems in physics in secondary school., M., Prosveshchenie, 1987, 336 p.

7. Kasyanov V.A. Physics. 10th grade, M., Bustard, 2002, 416 p.