In actual tasks in physics and mathematics, such values \u200b\u200bare often found as the volume, mass and density . Knowing the density and volume of the body or substance, absolutely permissible to detect it mass .

You will need

• - computer or calculator;
• - roulette;
• - dimensional capacity;
• - line.

Instruction

1. As pending, items that have the same volume, but made from various materials, will have a different mass (wood and metal, glass and plastic). The masses of bodies made from the same substance (without voids) are directly proportional to the volume of the subjects under consideration. In contrast, the continuous magnitude is the ratio of the mass of the subject to its volume. This value is the name "The density of the substance. In the future we denote her letter d.

2. Based on the definition, d \u003d m / v, where M is the mass of the subject (kg), V is its volume (m3). Claim is seen from the formula, the density of the substance is the mass of the unit of its volume.

3. Find out the density of the substance from which the subject is made from the density table in the appendix to the textbook of physics or on the site http://www.kristallallikov.net/page15.html, where densities are actually all existing substances.

5. If there is no likely to measure the geometric sizes of the body with accuracy, use the Archimedian law. To do this, take a vessel with a scale (or division) to measure the volume of the liquid, lower the object into water (in the vessel itself, equipped with divisions). The volume on the one that the contents of the vessel will increase - and there is the volume of the body immersed in it.

6. If the density d and the volume V of the object are carried out, consistently allowed to detect its mass, using the formula: m \u003d v * d. Before calculating the mass, bring all units of measurement into one system, say, in the international system of si measurement system.

7. The result from the above formulas Further: in order to obtain the desired mass value, knowing the density and volume, you need to multiply the value of the body volume to the density value of the substance from which it is made.

Mass body Traditionally define experimentally. For this take the cargo, put it on the scales and get the total measurement. But when solving the physical tasks given in the textbooks, the mass measurement on objective reasons is unrealistic, but there are those or other television data. Knowing this data allowed to determine the mass body implicitly by calculation.

Instruction

1. In school courses of physics, chemistry, astronomy is allowed to meet the representation of the mass. By weight body Find the inverse values \u200b\u200b- volume, density, strength. The mass is a quantitative indicator of the substance, in effect in the tasks in chemistry, the number of substances are found on the basis of the mass. The mass depends on the properties of the substance from which the body consists, as well as from the number of this substance. There are several basic methods of calculating the mass. Choose them depending on which other physical quantities are specified in the task. Let us see every case separately.

2. The most well-known method of finding the mass body - This is its calculation on the basis of volume and density. True, in a number of tasks, the volume itself is made before determining the mass, guided by other geometric bales body . For example, for a cylinder with the famous base areas and a height made from a substance with a density, the mass will be equal to: M \u003d? * V \u003d? * S * H, where Vc. \u003d S * H \u200b\u200b,? - density, S is the base area of \u200b\u200bthe cylinder, H is the cylinder height. If the volume is specified in the task directly, to find the mass of it is quite primitive to multiply to the density: M \u003d? * V

3. A different section of physics, where it is possible to calculate the mass - dynamics. Traditionally, the interaction between body mi, action of external forces on body , Body condition with uniform movement. Any body by force f gets a lifting when interacting with another body. At the same time, it is some m. The masses are associated with the power of a further relation: F \u003d M * A, where A is the loss of the specified body ; M-Massa body From here is allowed to know the lot body : m \u003d f / a

4. In chemistry textbooks, we meet the representations of the number of substances and molar mass. Through these two values, it is also allowed to express a lot of substances. From the fact that the number of substances is a physical value proportional to the number of particles, of which the substance consists, and the molar mass is the mass of one praying substance, calculate the mass of the specified number of this substance is allowed in a further way: MB \u003d MB * NB, where MB is a molar mass, NB-covered substances

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Helpful advice
An example of a problem for finding a body weight. Perhaps, given a small steel ball with a radius R \u003d 5 cm. Determine the mass of the ball, if it is famous that P is. \u003d 7.8 mg / m ^ 3. Initially detect the ball volume. It is equal: v \u003d 4? R ^ 2 \u003d 4 * 3.14 * 25 \u003d 314 cm ^ 3Mass is calculated in a further way: m \u003d p * v \u003d 7.8 * 314 \u003d 24.492

Density There is a ratio of mass to the volume occupied by it - for solid bodies, and the ratio of the molar mass to the molar volume - for gases. In the most universal form, the volume (or molar volume) will be the ratio of mass (or molar mass) to its density. Density Word. What to do? First, determine the mass, after that, calculate the volume, then make the necessary amendments.

Instruction

1. The volume of gas is equal to the ratio of the number of a substance multiplied by its molar mass - to a closer density. In other words, even knowing the density, you need to know the molar weight of the gas and the number of substances, that is, how many mol gas you have. In the thesis, knowing how much mol gas you have, allowed to calculate its volume, not even knowing density - according to the Avogadro law, one mol of all gas takes the volume of 22.4 liters. If you definitely calculate the volume through the density, then you will need to learn gas mass in the unknown yet.

2. The volume of solid body is allowed to determine, even not knowing the density, easily measuring it, and in the case of a difficult and dyewish incorrect form, the volume is determined, say, according to the volume of the solid body of the fluid. However, if it is necessary to calculate the volume through the density, the volume of the solid is the ratio of body weight to its density, and the mass is commonly determined by simple weighing. If weighing the body for some reason (let's say, it is too huge or moves) unthinkable, it will have to resort to sufficiently difficult indirect calculations. For example, for the moving body, the mass is the ratio of double kinetic energy to the square of its speed, or the relation of the force attached to the body, to its loss. For a somewhat large-sized body, it will have to be resorted to the calculations relative to the mass of the Earth, using the gravitational continuous and moment of rotation. Either - through the calculation of the specific heat capacity of the substance; In any case, the skill is only density to calculate the volume will be unsatisfactory.

3. Calculating the mass of solid body, allowed to calculate the volume - by simply dividing the mass to the density.

Note!
1. The above methods are more or less applicable only in the case of the homogeneity of the substance from which the solid body is consisting. The above methods are more or less applicable in a relatively close temperature range - from minus 25 to plus 25 degrees Celsius. With a change in the aggregate state of the substance, the density may vary hoppy; In this case, the formulas and methods of calculations will be at all.

Mass as a physical value is a parameter that characterizes the effect of body effects on gravity. To calculate body weight in physics It is necessary to know the two of its values: the density of the body material and its volume.

Instruction

1. Let a certain body of the volume V and the density of its substance p. Then it mass Count so: m \u003d p * v. For clarity, an example is given: let it give a 5 cubic aluminum bar. meters. Aluminum density is 2700 kg. / Cubic meters. meter. In this case, the mass of the bar will be: m \u003d 2700/5 \u003d 540 kg.

Note!
The representation of the mass is often confused with another, no less rarely encountered, physical value - weighing. Weight is measured in n / m? And characterizes the strength that affects the plot point. The mass of the same, in nature, does not have any point of the support, and acts as noted, only on the gravity of the Earth.

When solving some physical tasks you need to detect density body . Occasionally the density of the physical body needs to be determined in practice, let's say, in order to find out, it will drown it either. By the way, the human body is also allowed to attribute to physical bodies. Moreover, the presentation of the "density" of the human body a long time has long become more closely in use. So "the" firmly shot "man is traditionally called" dense ", and the one who has the opposite constitution of the body is" loose ".

You will need

• calculator, scales, ruler, measuring mug, density table of substances.

Instruction

1. In order to detect the density of the physical body, determine which substance or material it consists. After that, take the substance density table and detect the corresponding substance in it. So, let's say if the item is made of aluminum, its density will be 2.7 g / cm?.

2. If the body consists of several substances, then detect the density of all of them in the corresponding tables. In order to detect the density of the body in the aggregate, determine the contribution of the entire substance into the formation of the density of the subject. To do this, determine the volume of either the mass of the entire homogeneous part, and then consider the mass and volume of each body.

3. Let, say, the body consists of 2 parts weighing M1 and M2, respectively. The density of the whole part -? 1 and? 2. In order to detect the average body density, detect the universal volume: V \u003d V1 + v2 \u003d M1 *? 1 + m2 *? 2, and then divide to the universal body weight (m \u003d m1 + m2) :? \u003d V / M \u003d (M1 *? 1 + m2 *? 2) / (m1 + m2), where: V is the general volume of the body; V1 and V2 - the volume of the first and 2nd part of the body, respectively; m is the general mass of the body ; M1 and M2 - the mass of the first and 2nd part of the body, respectively ;? - average body density;? 1 and? 2 - the density of the first and 2nd part of the body, respectively.

4. If the volumes of the volume (V1 and V2) of the whole part of the body, as well as their density, use the similar formula to calculate the body's density :? \u003d V / M \u003d (v1 + v2) / (m1 + m2) \u003d (v1 + v2) / (V1 /? 1 + v2 /? 2). Designations of parameters are the same as in the previous formula.

5. If the material (substance), from which the body consists, uniformly has a non-permanent density (say, the tree, the density of which depends on the humidity), in order to detect its density, determine its volume and divide it. That is, use the formula :? \u003d V / M. For this, final, you will have to calculate either measure the volume and mass of the body, but this method will give the most accurate result. If the body has a formitive geometric shape form, consider its volume by using the appropriate stereometry formulas. The volume of difficult bodies determine through the volume of fluid supplanted by them. Body Mass Discover with Weighing Support.

Tip 6: How to detect a lot if the volume and density are famous

The mass of some body is its most important physical pallulation. In the current physical science there is a distinction between the submission of "mass": the gravitational mass (as a degree of body impact on earth gravity) and the inert mass (which effort will be needed in order to bring the body from the state of inertia). In any case detect mass Dyzhe is easy if famous density and body volume.

Instruction

1. In the event that the body is famous for such indicators as its volume (V) and density (p), then to calculate body weight, it will be necessary to apply the formula: m \u003d p * v.

2. For clarity, it is permitted to bring an example. Required to detect mass Concrete slab, whose volume is 15 m?.. Available: To find the mass of the concrete slab, it is necessary to know only it density . In order to find out this information, it is necessary to use the table of densities of different substances.

3. According to this table density Concrete is 2300 kg / m?. Then in order to detect mass Concrete slab, you will need to make a primitive algebraic effect: M \u003d 15 * 2300 \u003d 34500 kg, or 34.5 tons. Result: The mass of the concrete slab is 34.5 tons

4. The mass measurement by the traditional method occurs with one of the most ancient devices of society - with support for weights. This is due to the comparison of body weight with the imaginary reference mass of the cargo - Girus.

Note!
Conducting the calculation on the above formula, it is necessary to comprehend that thus learns the mass of rest of the body. Fascinating the fact that many elementary particles own a oscillating mass, which depends on the speed of their movement. If the elementary particle moves with the speed of the body, then this particle is a massless (say, photon). If the speed of the particle is below the speed of light, then such a particle is called cumbersome.

Helpful advice
When measuring the mass, it is never impossible to forget what the system will include a final result. It is in mind that in the system SI mass is measured in kilograms, while in the SSS system the mass is measured in grams. Also, the mass is measured in tons, centners, karats, pounds, oz, pounds, as well as in many other units, depending on the country and culture. In our country, for example, the mass has long been measured in pudges, burglaries, spools.

You have a two-toll barrel. You plan to fully fill with diesel fuel, which is used to heating with your mini-boiler room. And how much will it weigh, filled with solarium? Now we calculate.

You will need

• - table of specific density of substances;
• - Knowledge to make the simplest mathematical calculations.

Instruction

1. In order to detect a mass of the substance in its volume, use the specific density of the substance. P \u003d M / V. P - the specific density of the substance; m - its mass; v - occupied volume. We will consider the mass in grams, kilograms and tons. Volumes in cubic centimeters, decimeters and measures. And specific density, respectively, in g / cm3, kg / dm3, kg / m3, t / m3.

2. It turns out, under the terms of the task, you have a two-toll barrel. This means: a barrel with a capacity of 2 m3. It is called two-hundredthlylitone, as water, with its specific density equal to one, in such a barrel it includes 200 liters. The mass is worried. We investigate it in the presented formula for the first place. M \u003d P * VV in the right part of the formula is unfamiliar to the value of P - the specific density of diesel fuel. Discover it by directory. Even easier - to ask a request in the Internet "Specific density of diesel fuel".

3. Detected: the density of summer diesel fuel at T \u003d +200 C - 860 kg / m3. Present values \u200b\u200bin the formula: M \u003d 860 * 2 \u003d 1720 (kg) 1 ton and 720 kg - so much weigh 200 liters of summer diesel fuel. Veneered barrel in advance, allowed to calculate the universal weight and estimate the power of the rack under the barrel with the solarium.

4. In rural areas, it is suitable in advance to calculate the mass of the firewood in the cube, in order to decide on the carrying capacity of the transport on which these firewood will be delivered. For example, you need a minimum of 15 cubic meters for the winter. Meters of birch firewood. Look in the reference literature the density of birch firewood. This is: 650 kg / m3. Call the mass, substituting the values \u200b\u200bin the same specific density formula. M \u003d 650 * 15 \u003d 9750 (kg) Now, based on the carrying capacity and capacity of the body, you can decide on the type of vehicle and the number of trips.

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Note!
A older people are greatly familiar with the presentation of specific gravity. The specific density of the substance is the same as the proportion.

There are settings when you need to calculate mass liquids contained in some tank. It may be during the training session in the laboratory, and during the solution of household strokes, let's say, when repairing either painting.

Instruction

1. The easiest way is to resort to weighing. Initially, weigh the container together with the liquid, then reconnect the liquid into a different container suitable in size, and weigh the empty container. And then it remains only to find out of the greater value, and you will receive the result. Of course, it is allowed to resort to this method, only by dealing with unusual liquids, which later overflow actually do not remain on the walls and the bottom of the first container. That is, some number and then will remain, but it will be a little thing that it is allowed to neglect, it will not immediately affect the accuracy of the calculations.

2. And if the liquid is viscous, say, glycerin? How then to determine it mass ? In this case, you need to know its density (?) And occupied volume (V). And then close everything is elementary. Mass (m) is calculated by the formula M \u003d? V. Of course, before the calculation you need to translate the factors to the solid system of units.

3. Density liquids Delivered to detect in the physical or chemical directory. But it is cool to use the measuring instrument - a density meter (densitometer). And the volume is allowed to calculate, knowing the shape and dimensions of the container (if it has a true geometric shape). For example, if the same glycerin is in a cylindrical barrel with the diameter of the base D and height H, then the volume of the barrel is calculated by the formula :? D ^ 2H / 4.

4. Imagine, such a task is asked. During the laboratory experiment, the liquid mass M, which is in the calorimeter tank and having the heat capacity C was heated from the initial temperature T1 to the final temperature T2. The number of heat was spent on this heating, equal to Q. What is the mass of this liquids ?

5. All the values, in addition to M, are famous, heat loss during the experiment is allowed to neglect. There is no definitely nothing difficult in the calculation. It is only necessary to recall the formula that combines the number of heat, mass liquids , its heat capacity and difference in temperatures. It is as follows: Q \u003d Mc (T2-T1). Incidentally, mass liquids It is calculated by the formula: M \u003d Q / C (T2-T1). Substituting in the formula of the vast values, you can easily calculate mass liquids m.

The value of a continuous plate, denoted by the letter H, is determined experimentally in the laboratory with an accuracy of ten characters later. Put the skill for its definition is allowed in the physical office, but the accuracy will be much smaller.

You will need

• - a photocell with an external photo effect;
• - light source with monochromator;
• - smoothly adjustable power supply by 12 V;
• - voltmeter;
• - microammeter;
• - Lamp at 12 V, 0.1 A;
• - Calculator operating with the numbers presented in exponential form.

Instruction

1. Use a photocell to skill with an external photoelectric effect. An element with an internal photoeffect (i.e., not vacuum, and semiconductor) will not fit. Experience it on the suitability for holding the skill, for which you connect to the microamermeter at easy, observing polarity. Direct the light on it - the arrow must deviate. If this does not happen, use a different type of photocell.

2. Without changing the polarity of the connection or a photocell, nor a microammeter, burst the circuit and turn on the adjustable power source in its opening, the output voltage is allowed to smoothly change from 0 to 12 V (with two handles for supper and accurate adjustment). ATTENTION: Include this source should not be direct, but in reverse polarity, in order not to increase its voltage, but reduced the current through the element. In parallel, it is connected to the voltmeter - for the polarity, corresponding to the symbols at the source. This is allowed not to do if the block has a built-in voltmeter. Also connect parallel to the output load, say, in the form of a lamp by 12 V, 0.1 A, in case the internal resistance of the source is large. Light lamps should not fall on the photocell.

3. Set the source voltage to zero. Direct the flow of light from the source with a monochromator into the photocell, exposing the wavelength of about 650 nanometers. Smoothly increasing the power supply voltage, achieve, in order to the current through the microammmetrometer became zero. Leave the regulator in this location. Record Voltmeter and Monochromator Scale.

4. Place on a monochromator wavelength of about 450 nanometers. Increase the output voltage of the power supply, in order to the current through the photocell again became zero. Write down new voltmeter readings and monochromator scales.

5. Calculate the frequency of light in Hertz for the first and second skills. To do this, divide the speed of light in a vacuum, equal to 299792458 m / s, the wavelength, translated from nanometers in advance. For simplicity, consider the refractive index of the air equal to 1.

6. Remove more voltage from smaller. The result multiply an electron to 1,602176565 (35) · 10 ^ (35) (35) · 10 ^ (? 19) (CL), and then divide the subtraction of a larger frequency of less. It turns out a continuous plank, expressed in Joules, multiplied by a second (J · C). If it is close to an official value equal to 6,62606957 (29) · 10 ^ (- 34) J · C, the skill is allowed to consider positively.

Video on the topic

Note!
Be careful when working with electrical equipment.

Many of us were asked for school hours: "How to find a body weight"? Now we will try to answer this question.

Finding the mass through its volume

Suppose you have a barrel on two hundred liters. You intend to fully fill it with diesel fuel used by you for heating your small boiler room. How to find a lot of this barrel filled with diesel fuel? Let's try to solve this simplest task with you at first glance.

Solve the task, substances through its volume, quite easily. To do this, apply the solid density formula

where P is a specific density of the substance;

m - its mass;

v - occupied volume.

Grams, kilograms and tons will be used. MEASURES: Cubic centimeters, decimeters and meters. The specific density will be calculated in kg / dm³, kg / m³, g / cm³, t / m³.

Thus, in accordance with the terms of the task, at our disposal there is a barrel of two hundred liters. This means that its volume is 2 m³.

But you want a lot. It is derived from the above formula like this:

First, we need to find the value of P - the specific finding this value, using the directory.

In the book we find that p \u003d 860.0 kg / m³.

Then we substitute the values \u200b\u200bin the formula:

m \u003d 860 * 2 \u003d 1720.0 (kg)

Thus, the answer to the question of how to find a lot was found. One ton and seven hundred twenty kilograms is the weight of two hundred liters of summer diesel fuel. Then you can make the approximate calculation of the total weight of the barrel and the power of the rack under the barrel with the solarium.

Finding a mass through density and volume

Very often in practical tasks in physics, you can meet such values \u200b\u200bas weight, density and volume. In order to solve the task how to find a body weight, you need to know its volume and density.

Items that you will need:

1) Roulette.

2) Calculator (computer).

3) Measurement capacity.

4) line.

It is known that items with an equal volume, but made of various materials, will be a different mass (for example, metal and wood). The masses of bodies, which are made of a certain material (without voids), are directly proportional to the volume of the subjects under consideration. Otherwise, the constant is the ratio of mass to the volume of objects. This indicator is called the "density of a substance". We will denote it to the letter d.

Now it is required to solve the problem, how to find a mass in accordance with the formula d \u003d m / v, where

m is a mass of the subject (in kilograms),

V is its volume (in cubic meters).

Thus, the density of the substance is a mass of its volume.

If you need to find from which the subject is created, you should use the density table, which can be found in a standard textbook in physics.

The volume of the subject is calculated by the formula V \u003d H * S, where

V - volume (m³),

H - the height of the subject (M),

S is the base area of \u200b\u200bthe subject (m²).

In the event that you cannot clearly measure the geometric parameters of the body, then you should resort to the help of Archimedes laws. To do this, you need a vessel that has a scale that serves to measure the volume of liquids and lower the object into water, that is, a vessel on which there are divisions. The volume to which the contents of the vessel will be increased is the body volume that is immersed in it.

Knowing the volume V and the density D of the subject, you can easily find its mass by the formula M \u003d D * V. Before calculating the mass, it is required to obtain all measuring units into a single system, for example, in a system that is an international measuring system.

In accordance with the above formulas, you can draw the following conclusion: To find the required amount of mass with a known volume and known density, you need to multiply the value of the density of the material from which the body is made to the volume of the body.

In chemistry, it is not without a mass of substances. After all, this is one of the most important parameters of the chemical element. On how to find a lot of substances in various ways, we will tell you in this article.

First of all, it is necessary to find the desired element, using the Mendeleev table, which can be downloaded on the Internet or buy. Fractional numbers under the element sign are its atomic mass. It must be multiplied by the index. The index shows how many element molecules are contained in this substance.

1. When you have a complex substance, then you need to multiply the atomic mass of each element of the substance to its index. Now it is necessary to fold the atomic masses you received. Such a mass is measured in grams / mol (g / mol). How to find a molar mass of substance, we will show on the example of calculating the molecular weight of sulfuric acid and water:

   H2SO4 \u003d (H) * 2 + (s) + (O) * 4 \u003d 1 * 2 + 32 + 16 * 4 \u003d 98g / mol;

   H2O \u003d (H) * 2 + (O) \u003d 1 * 2 + 16 \u003d 18g / mol.

   The molar mass of simple substances that consist of one element is calculated by the same way.

2. You can calculate the molecular weight along the existing table of molecular masses, which can be downloaded on the Internet or purchase in a bookstore
3. It is possible to calculate the molar mass with the help of formulas and equate it to the molecular weight. The units of measurement should be changed from "g / mol" on "A.M.".

   When, for example, you know the volume, pressure, mass and temperature on the Kelvin scale (if Celsius, then it is necessary to translate), then you can find out how to find a molecular weight of the substance by using the Mendeleev-Kilperon equation:

   M \u003d (M * R * T) / (P * V),

   where R is a universal gas constant; M is a molecular (molar mass), A.E.M.

4. Calculate the molar mass is possible with the help of the formula:

   where n is the amount of substance; M is the mass of this substance. Here it is necessary to express the amount of substance using the volume (n \u003d V / Vm) or the Avogadro number (N \u003d N / Na).

5. If the value of the gas volume is given, then it is possible to find its molecular weight by taking a hermetic cylinder with a known volume and pumping air from it. Now you need to weigh the cylinder on the scales. Next, download gas in it and weigh again. The difference between the masses of the empty cylinder and the cylinder with gas is the mass of the gas you need.
6. When you need to carry out a cryoscopy process, it is necessary to calculate the molecular weight by the formula:

   M \u003d p1 * ek * (1000 / p2 * Δtk),

   where P1 is a mass of a dissolved substance, r; P2 is a mass of solvent, r; EK is a cryoscopic solvent constant, which can be found from the corresponding table. This constant is different for different liquids; ΔTK is the temperature difference that is measured using a thermometer.

Now you know how to find a mass of substances, be it simple or difficult, in any aggregate state.

Many of us were asked for school hours: "How to find a body weight"? Now we will try to answer this question.

Finding the mass through its volume

Suppose you have a barrel on two hundred liters. You intend to fully fill it with diesel fuel used by you for heating your small boiler room. How to find a lot of this barrel filled with diesel fuel? Let's try to solve this simplest task with you at first glance.

Solve the task how to find a mass of substances through its volume is quite easy. To do this, apply the solid density formula

where P is a specific density of the substance;

m - its mass;

v - occupied volume.

As a measure of mass, grams, kilograms and tons will be used. MEASURES: Cubic centimeters, decimeters and meters. The specific density will be calculated in kg / dm³, kg / m³, g / cm³, t / m³.

Thus, in accordance with the terms of the task, at our disposal there is a barrel of two hundred liters. This means that its volume is 2 m³.

But you want to know how to find a lot. It is derived from the above formula like this:

First, we need to find the value of the P - specific density of diesel fuel. You can find this value using the directory.

In the book we find that p \u003d 860.0 kg / m³.

Then we substitute the values \u200b\u200bin the formula:

m \u003d 860 * 2 \u003d 1720.0 (kg)

Thus, the answer to the question of how to find a lot was found. One ton and seven hundred twenty kilograms is the weight of two hundred liters of summer diesel fuel. Then you can make the approximate calculation of the total weight of the barrel and the power of the rack under the barrel with the solarium.

Finding a mass through density and volume

Very often in practical tasks in physics, you can meet such values \u200b\u200bas weight, density and volume. In order to solve the task how to find a body weight, you need to know its volume and density.

Items that you will need:

1) Roulette.

2) Calculator (computer).

3) Measurement capacity.

4) line.

It is known that items with an equal volume, but made of various materials, will be a different mass (for example, metal and wood). The masses of bodies, which are made of a certain material (without voids), are directly proportional to the volume of the subjects under consideration. Otherwise, the constant is the ratio of mass to the volume of objects. This indicator is called the "density of a substance". We will denote it to the letter d.

Now it is required to solve the problem, how to find a mass in accordance with the formula d \u003d m / v, where

m is a mass of the subject (in kilograms),

V is its volume (in cubic meters).

Thus, the density of the substance is a mass of its volume.

If you need to find the density of the material from which the subject is created, you should use the density table, which can be found in a standard textbook in physics.

The volume of the subject is calculated by the formula V \u003d H * S, where

V - volume (m³),

H - the height of the subject (M),

S is the base area of \u200b\u200bthe subject (m²).

In the event that you cannot clearly measure the geometric parameters of the body, then you should resort to the help of Archimedes laws. To do this, you need a vessel that has a scale that serves to measure the volume of liquids and lower the object into water, that is, a vessel on which there are divisions. The volume to which the contents of the vessel will be increased is the body volume that is immersed in it.

Knowing the volume V and the density D of the subject, you can easily find its mass by the formula M \u003d D * V. Before calculating the mass, it is required to obtain all measuring units into a single system, for example, in a system that is an international measuring system.

In accordance with the above formulas, you can draw the following conclusion: To find the required amount of mass with a known volume and known density, you need to multiply the value of the density of the material from which the body is made to the volume of the body.

Instruction

To find a mass, knowing the density, divide the volume of the body or substance to its density. That is, use the formula: M \u003d V / ρ, where: V is the volume,
ρ - density,
V - volume. Perfect the mass by calculating the mass. Give all units of measurement into one system, for example, in an international measurement system (C). To do this, translate the volume (m³), and the density is in on (kg / m³). In this case, the mass value will turn out in kilograms.

If the density and volume are specified in one units system, then the preliminary in si is optional. The mass of the body or substance in this case will be measured in the unit, which is specified in the numerator unit of the density measurement unit (the unit of measurement of the volume during the calculation is reduced).
For example, if the volume is set in liters, and the density in grams per liter, then the calculated mass will turn out in grams.

If the volume of the body (substance) is unknown or not specified explicitly in the conditions of the task, then try to measure it, calculate or find out using indirect (optional) data.
If the substance is a bulk or liquid, then it is usually located in a container that usually has a standard volume. For example, the volume of the barrel is usually equal to 200 liters, the volume of buckets - 10 liters, the volume of glass is 200 milliliters (0.2 liters), the volume of the tablespoon is 20 ml, the volume of tea-5 ml. The volume of three-liter and liter cans is not difficult to guess from their name.
If the liquid takes not the entire container or the container is non-standard, then overripe it into another container, the volume is known.
If there is no suitable container, break the fluid using a measuring mug (banks, bottles). In the process of liquid fraction, simply count the number of such circles and multiply the volume of the measuring container.

If the body has a simple form, then calculate its volume using the appropriate geometric formulas. For example, if the body has the shape of a rectangular parallelepiped, then its volume will be equal to the product of its lengths. That is: VPr.Par. \u003d A * B * C, where: VPr.Par. - the volume of rectangular parallelepipeda, and
a, B, C - the values \u200b\u200bof its length, widths and heights (thickness), respectively.

If the body has a complex geometric shape, then try (conditionally!) To split it into a few more parts, find the volume of each of them separately and then fold the obtained values.

If the body cannot be divided into simpler figures (for example, a statuette), then use the Archimedes technique. Lower the body into water and measure the volume of the displaced fluid. If the body does not sink, then "clutch" it with a thin stick (wire).
If the volume of water displaced to calculate is problematic, then weigh the outlined water, or find the difference between the initial and remaining mass of water. At the same time, the number of water kilograms will be equal to the number of liters, the number of grams - the number of milliliters, and the number of tons - the number of cubic meters.