What is the difference between mass and... What is the difference between weight and mass? Two characteristics of an item

In life, we very often say: “weighs 5 kilograms,” “weighs 200 grams,” and so on. And at the same time we don’t know that we are making a mistake when we say this. The concept of body weight is studied by everyone in the physics course in the seventh grade, but the erroneous use of some definitions has become so mixed up in us that we forget what we have learned and believe that body weight and mass are one and the same thing.

However, this is not true. Moreover, body weight is a constant value, but body weight can change, decreasing down to zero. So what is the mistake and how to speak correctly? Let's try to figure it out.

Body weight and body weight: calculation formula

Mass is a measure of the inertia of a body, it is how the body reacts to an impact applied to it, or itself affects other bodies. And the weight of a body is the force with which the body acts on a horizontal support or vertical suspension under the influence of the Earth’s gravity.

Mass is measured in kilograms, and body weight, like any other force, is measured in newtons. The weight of a body has a direction, like any force, and is a vector quantity. But mass has no direction and is a scalar quantity.

The arrow that indicates body weight in pictures and graphs is always directed downward, just like gravity.

Body weight formula in physics is written as follows:

where m is body mass

g - acceleration free fall= 9.81 m/s^2

But, despite the coincidence with the formula and direction of gravity, there is a serious difference between gravity and body weight. The force of gravity is applied to the body, that is, roughly speaking, it presses on the body, and the weight of the body is applied to the support or suspension, that is, here the body presses on the suspension or support.

But the nature of the existence of gravity and the weight of a body is the same as the attraction of the Earth. Strictly speaking, the weight of a body is a consequence of the force of gravity applied to the body. And, just like gravity, body weight decreases with increasing altitude.

Body weight in zero gravity

In a state of weightlessness, body weight equal to zero. The body will not put pressure on the support or stretch the suspension and will not weigh anything. However, it will still have mass, since in order to give the body any speed, it will be necessary to apply a certain force, the greater the greater the mass of the body.

Under the conditions of another planet, the mass will also remain unchanged, and the weight of the body will increase or decrease, depending on the strength of the planet’s gravity. We measure body mass with scales, in kilograms, and to measure body weight, which is measured in Newtons, you can use a dynamometer, a special device for measuring force.

In the section on the question: what is the difference between mass and weight? given by the author I-beam the best answer is IN modern science weight and mass - absolutely different concepts: mass is an integral property of the body, and weight is the result of the action of gravity on the support. At the same time, they learned about the difference in weight and mass relatively recently, and in many everyday situations the word "weight" continues to be used when in fact we're talking about about "mass". For example, we say that an object "weighs one kilogram" even though a kilogram is a unit of mass.
Since gravity at the poles differs only slightly from gravity at the equator, the distinction between mass and weight is not important for many practical purposes. In such a constant gravitational field, the gravitational force acting on an object is directly proportional to its mass. So, if object A weighs 10 times more than object B, then object A weighs 10 times more than object B. For example, when we buy a bag of sugar, we can estimate its weight and be sure that it is good indicator quantities, although what we really need to know is how much sugar is in the bag. However, minor fluctuations in the Earth's gravitational field do exist. These changes the relationship between weight and mass, and must be taken into account when measuring weight with high accuracy. The difference between mass and force becomes apparent when objects are compared in different gravitational fields: those who are far from earth's surface. For example, on the surface of the Moon, gravity is only about one-sixth that of Earth. A person weighing 60 kilograms would weigh on the Moon as a load weighing 10 kilograms on Earth.
Source: Wikipedia

Reply from Tenant[newbie]
Yes

Reply from dry up[active]
Mass is the amount of substance contained in a body.
The weight-force with which the body presses on the support is measured in Newtons, by the way, for convenience in everyday life in kg!

Reply from No Title[active]
m=m, and weight is m*g!

Reply from Anastasia Boldyreva[newbie]
mass is the mass, measured in kg, and weight is the force with which the mass acts on the support, measured in newtons. It’s just that it is usually assumed that the action takes place on Earth, and therefore the multiplication by the acceleration of gravity is omitted. They say not a weight of 98 newtons (10kg * 9.8), but a weight of 10 kg, meaning the force with which 10 kg presses on a support on the surface of the Earth.
In zero gravity, weight disappears, but mass remains.

Reply from The visitor from the past[guru]
The connection between these concepts is described by Comrade Isaac Newton's 2nd law.
F = m*g, where F is weight, that is, the force with which a body of mass m is attracted to Mother Earth. g is the acceleration due to gravity, equal to approximately 9.81 m/s^2. Moreover, the acceleration in different points Lands are different. For example at the pole
g = 9.832 m/s^2, and at the equator g = 9.78 m/s^2. This means that the body has constant mass, will weigh more at the pole than at the equator. These are the pies.
Good luck and success to you!!!

Which word do you use more often: “mass” or “weight”? I think it depends on your profession. If you are a physics teacher, then the word “mass” appears more often in your speech. If you are a salesperson in a store, then you hear and say the word “weight” many times a day. What is the difference between mass and weight and what does it have to do with it? professional activity? Mass and weight are synonyms, but not absolute. To begin with, both words have several meanings. This is easy to see by the example of such phrases: “the weight of your voice”, “the weight of the load”, “a lot of differences”, “body weight”. The basic meanings of these words in everyday life are the same, but in science, especially in physics, the differences between mass and weight are significant. So, weight- This physical quantity, which determines the inertial and gravitational properties of bodies. Mass determines the amount of substance in an object. Weight- this is the force with which an object presses on a support in order not to fall. Based on this definition, we come to the conclusion that in the case of weight, the gravitational component is mandatory for giving correct definition. So, for example, if an astronaut’s weight on earth is 80 kg, then his weight in orbit will be almost zero; on the Moon he would weigh less than 15 kg, but on Jupiter - almost 200 kg. Moreover, its mass remains unchanged in all cases.
Officially, the mass and weight are various units measurements, mass - kilograms, weight - newtons. It is interesting that in medicine we traditionally deal with the concept of “human weight”, “newborn weight”, which is measured in kilograms, that is, in fact we are talking about mass. Moreover, mass does not imply the action of any forces, like weight. This is a value that is calculated in a state of rest and inertia.

Here are the significant differences between weight and mass highlighted by TheDifference.ru:

Mass is a fundamental physical quantity that determines the amount of matter and the inert properties of a body. Weight is the force with which an object presses on a support, which depends on gravity. For example, the mass of a person is different planets remains the same, but the weight changes depending on gravity.
Mass is usually measured in kilograms, weight - in newtons.

Mass and weight are synonyms, but not absolute. Mass is a physical quantity that determines the inertial and gravitational properties of bodies. Mass determines the amount of substance in an object. Weight is the force with which an object presses on a support or stretches a suspension.

Weight and mass. How are they different? What's the difference?

Weight measured in kilograms and weight in newtons.
Weight is the product of mass and the acceleration of gravity (P = mg). Weight value (at constant mass body) is proportional to the acceleration of gravity, which depends on the height above the earth's (or other planet's) surface. And to be even more precise, weight is a particular definition of Newton’s 2nd law - force is equal to the product of mass and acceleration (F=ma). Therefore, it is calculated in Newtons, like all forces.
Weight- a constant thing, but weight is variable and depends, for example, on the height at which the body is located. It is known that with increasing height, the acceleration of gravity decreases, and the weight of the body decreases accordingly, under the same measurement conditions. Its mass remains constant.

We answered the question: “mass and weight - how are they different?” To better understand the topic, let’s look at an example of the difference between weight and mass. To do this, let's take a closer look at our world, in which the Earth's gravitational force has disappeared.

Weight and mass are differences in zero gravity conditions.

Let a large loaded carriage stand on the rails without gravity in our world and let the friction in its wheels be as low as possible - ball bearings and perfectly smooth rails are made. Do you think it will be easy to move such a carriage here and accelerate it to high speed? And if he is moving, will it be easy to stop him quickly?

It turns out that this still requires a decent amount of force. How so, why? – you ask. After all, the carriage weighs nothing and we just saw that you can easily hold it on your shoulders? Yes, but holding a lifted object motionless is one thing, but moving it from its place, setting it in motion and increasing speed (accelerating) is another. The first depends on weight, that is, the force of gravity of the Earth, and the second on mass.

In a world without the Earth's gravity, weight disappears, but mass remains. This is the difference between weight and mass.

If we were in a world without gravity, we would notice one important thing. We ourselves and all objects fly up here from the shocks. But the items low mass- pencils, dishes, books - take off from weak shocks and with significant acceleration. And to move and make a massive cabinet or a factory machine fly, you need much great strength, and their speed will increase very slowly.

Remember the mechanic at the depot. He managed, by pushing from below, to force the locomotive to rise above the floor. But how slowly the wheels separated from the rails and with what low speed the massive machine floated upward. At the same time, in order to speed up the movement, it was necessary to strain with all one’s might. It’s not easy to stop a giant rushing upward and then direct it back down. It is also difficult to accelerate or stop a carriage here that has lost weight but retained its enormous mass.

In a world without gravity, but with remaining mass, bodies by inertia retain not only a state of rest, but also movement.

It’s good that, having pushed off the floor and flew up, you hit the ceiling and your movement stopped. If this happened on the street, by inertia you would fly further and further from the Earth into outer space.

Observing the chaos reigning in a room or on the street, we notice that small objects, such as your shoes or vegetables from a stall, are carried around with high speed. Massive cabinets or trucks slowly float between them. Here, in fact, what was important was the greater or lesser acceleration that informed this various masses the action of even the same forces. After all, the same diesel locomotive will accelerate 20 cars faster and to a higher speed than a train consisting of 50 cars.

While floating around the room, beware of colliding with a piano flying towards you: although it weighs nothing, it has large mass and can hit you with considerable force.

So, let's not confuse two different things: mass and weight - the amount of matter that has inertia, and the force with which this mass is attracted by the Earth. Let us remind you again: this is the difference between weight and mass, this is the difference between mass and weight.

There are no “worlds without gravity” in nature - we could only imagine the Earth having ceased to attract. But in the Universe there are worlds of “low and high gravity” - celestial bodies, attracting with different strengths.

The mass of a person on different planets remains the same, but the weight changes depending on the force of gravity. So, for example, if weight An astronaut on earth weighs 80 kg, then his weight in orbit will be almost zero; on the Moon he would weigh less than 15 kg, but on Jupiter - almost 200 kg. At the same time, his weight remains unchanged in all cases. This topic is covered in the following articles.

Mass and weight. Weight and mass. Probably, most often these two completely different concepts are compared, or even taken for the same thing. After all, we really say: “How much do you weigh?” when, in fact, we only mean quantitative properties our body, without really thinking about any others additional interactions, which may imply such ambiguous word formations. Therefore, in order not to get confused in definitions, it is best to understand why mass cannot be weight.

Very unexpected kilograms

Those numbers that appear on the scales after, for example, putting a bag of strawberries there or trying to fit a whale, not only help determine how much money you need to pay for delicious berries or find out whether the whale is really as big as they say it is , but also reveal many other features.

If we assert scientific language, That mass is a physical quantity, which is a measure of a body’s gravity, energy and inertia, which naturally entails certain characteristics from the point of view of classical mechanics:

Mass (m) is invariant: it does not depend on the choice of the reference system (FR), that is, a passenger on a train or plane will not suddenly lose weight or gain weight while moving. vehicle. Such relativity of CO is inherent, for example, in determining speed, but not mass, which does not change so dramatically.
Mass does not depend on the speed of the body. At the same time, inertia is the property of spending certain time to change speed, it is the mass that determines. For an elephant, for example, it is very difficult to instantly accelerate. He will take steps that are stable and comfortable for him, and just show the mouse the cat - and only then will he be seen. It is less inert than an elephant and changes speed faster.
Also, when two bodies interact, their masses are inversely proportional to the acceleration ratio, which is also a matter of inertia. This discovery helped determine the masses of planets, satellites and other cosmic bodies, since doing this in any other way is almost impossible.
Mass is additive: the entire mass of a body is equal to the masses of all its parts.
The law of conservation of mass exists and is fulfilled - this means that no matter what processes occur in any harmonious system, total mass always remains the same.

At the same time, any body can gravitationally interact with other bodies. This feature is called gravitational mass who received her main wording when studying the force of gravity. Gravitational interaction two bodies is directly proportional to the product of their masses.

Einstein proved that any body that has mass also has its own supply of energy (E). If mass decreases or increases, the same happens with energy - E = mс², where c is the speed of light.

And yet the weight

Weight (P) is a measurement of nothing more than the force exerted by a body on a support, as a result of the Earth's gravity. Moreover, if this same support is at rest or moves uniformly in a straight line, then the weight equal to force attraction – P = mg, where m is the mass of the body, g ≈ 9.81 is the acceleration of gravity.

Simply put, weight measures how hard we press on the surface of where we stand or sit.
If the body moves with acceleration, then the weight will be determined taking it into account: P = m(g+a) - during movement vertically upward, P = m(g-a) - vertically downward.

Overweight (weight gain) is a rather interesting phenomenon, as it can affect a person’s condition: there is a short-term loss of vision and difficulty breathing. Overweight happens to astronauts during takeoff and landing spaceship, with pilots doing maneuvers (loops).

Weightlessness is a state of a body in which weight is zero, due to the fact that the force of gravity imparts equal acceleration to the body and its support. This is how weight “disappears” for an astronaut while in orbit. To feel this, you can just jump. Then there will be no support under your feet.