1. what energy transformations occur when a body rises and when it falls?
2.what happens to the mechanical energy when a lead weight hits a lead plate?
3.what energy is called the internal energy of the system?
4. how the internal energy of a gas changes during its expansion; when it is compressed? give examples
5. Does a body whose temperature is 0 degrees Celsius have internal energy?
6. the same substance can be in a solid, liquid, or gaseous state. In which state is the internal energy of the body greater? less?

A tube with a volume of 0.5 m3 is filled with neon weighing 0.45 kg. What is the density of this gas? 1)1.11

3) 0.225 kg/m3

Compare the densities of the substances from which they are madecubes 1 and 2.

4) densities cannot be compared

There are 23 particles in the sodium nucleus. Of these, 12 are neutrons. How many protons are there in the nucleus?

1)11 protons

2) 35 protons

3) 10 protons

4) 23 protons

Pressure is a value equal to:

1) the ratio of the force acting perpendicular to the surface to the area of ​​this surface

2) the product of the force acting perpendicular to the surface and the area of ​​this surface

3) the ratio of surface area to the force acting perpendicular to this surface

4) the product of the square of the force acting perpendicular to the surface and the area of ​​this surface

Which physical phenomenon lies at the heart of the deviceand work mercury thermometer?

1) melting solid when heated

2) convection in liquid when heated

3) expansion of liquid when heated

4) evaporation of liquid

Please indicate the correct endings for the phrases:

The boiling point of a liquid...

a) increases with atmospheric pressure

Liquid evaporation temperature…

b) decreases with increasing atmospheric pressure

Liquid condensation temperature...

c) does not depend on atmospheric pressure

How does the internal energy of a substance change whentransition from solid to liquid at constant temperature?

1) varies differently for different substances

2) can increase or decrease depending on external conditions

3) remains constant

4) increases

Which physical parameter determines the amount of heat required to convert 1 kg of liquid into vapor at boiling point?

1) specific heat of combustion

2) specific heat of vaporization

3) specific heat of fusion

4) specific heat capacity

Internal energy steel ball will change if:

1) raise it above the ground;

2) throw it horizontally;

3) hit it hard with a hammer;

4) cannot be changed.

Which speed is greater: 20 m/s or 72 km/h?

3) they are equal;

4) impossible to determine.

Which answer option correctly indicates the order of the missing words in the sentence?

Protons have... a charge, and neutrons...

1) positive, negative;

2) positive, have no charge;

3) negative, positive;

4) negative, have no charge.

What causes friction?

1) roughness of the surfaces of contacting bodies;

2) mutual attraction of molecules of contacting bodies;

3) surface roughness or mutual attraction of molecules of contacting bodies;

4) among answers 1-3 there is no correct one.

The water began to turn into ice. During further crystallization its temperature:

1) will increase;

2) will decrease;

3) will not change;

4) will first increase, then decrease.

The unit of electrical resistance is:

1) 1 Cl; 2) 1 Ohm; 3) 1 A; 4) 1 V.

Electrical voltage is calculated using the formula:

1) U = R/I; 2) U = I/R; 3) U = I R; 4) I = U/R.

The current in the circuit will decrease if:

3) resistance will decrease;

4) current does not depend on voltage and resistance.

How will the pressure change if the pressure force is doubled and the area is reduced by a factor of 2?

1) will decrease by 4 times; 2) will decrease by 2 times;

3) will increase by 2 times; 4) will increase 4 times.

The internal energy of bodies depends on:

1) body speed;

2) body temperature;

3) body shape;

4) body volume.

Type of train movement when approaching the station:

1) free fall;

2) slowdown;

3) accelerated;

4) uniform.

Which of the following substances has the lowest thermal conductivity?

1) hard; 2) liquid;

3) gaseous; 4) solid and liquid.

The attachment has everything...

A wooden block was placed on the bottom of an aquarium with water and released. How does the potential energy of the block change as it floats up? How does it change

at the same time potential energy water? How does the sum of the potential energy of the block and water change? Do not take into account water resistance.

Internal body energy cannot be a constant value. It can change in any body. If you increase the body temperature, then its internal energy will increase, because the average speed of molecular movement will increase. Thus, the kinetic energy of the molecules of the body increases. And, conversely, as the temperature decreases, the internal energy of the body decreases.

We can conclude: The internal energy of a body changes if the speed of movement of the molecules changes. Let's try to determine what method can be used to increase or decrease the speed of movement of molecules. Consider the following experiment. Let's attach a brass tube with thin walls to the stand. Fill the tube with ether and close it with a stopper. Then we tie it with a rope and begin to move the rope intensively in different sides. After a certain time, the ether will boil, and the force of the steam will push out the plug. Experience demonstrates that the internal energy of the substance (ether) has increased: after all, it has changed its temperature, at the same time boiling.

The increase in internal energy occurred due to the work done when the tube was rubbed with a rope.

As we know, heating of bodies can also occur during impacts, flexion or extension, or, more simply, during deformation. In all the examples given, the internal energy of the body increases.

Thus, the internal energy of the body can be increased by doing work on the body.

If the work is performed by the body itself, its internal energy decreases.

Let's consider another experiment.

We pump air into a glass vessel that has thick walls and is closed with a stopper through a specially made hole in it.

After some time, the cork will fly out of the vessel. At the moment when the stopper flies out of the vessel, we will be able to see the formation of fog. Consequently, its formation means that the air in the vessel has become cold. The compressed air that is in the vessel does a certain amount of work when pushing the plug out. This work he performs due to his internal energy, which at the same time is reduced. Conclusions about the decrease in internal energy can be drawn based on the cooling of the air in the vessel. Thus, The internal energy of a body can be changed by performing certain work.

However, internal energy can be changed in another way, without doing work. Let's consider an example: water in a kettle that is standing on the stove is boiling. The air, as well as other objects in the room, are heated by a central radiator. IN similar cases, internal energy increases, because body temperature increases. But the work is not done. So, we conclude a change in internal energy may not occur due to the performance of specific work.

Let's look at another example.

Place a metal knitting needle in a glass of water. Kinetic energy of molecules hot water, more than the kinetic energy of cold metal particles. The hot water molecules will transfer some of their kinetic energy to the cold metal particles. Thus, the energy of the water molecules will decrease in a certain way, while the energy of the metal particles will increase. The water temperature will drop, and the temperature of the knitting needle will slowly will increase. In the future, the difference between the temperature of the knitting needle and the water will disappear. Due to this experience, we saw a change in internal energy different bodies. We conclude: The internal energy of various bodies changes due to heat transfer.

The process of converting internal energy without performing specific work on the body or the body itself is called heat transfer.

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There are ways to change the internal energy of a body: work and heat transfer.

When work is performed, it changes in two cases: during friction and during inelastic deformation. When work is done by friction force, the internal energy increases due to a decrease mechanical energy, the rubbing bodies heat up. In the case of inelastic compression of a body, its internal energy increases due to a decrease in mechanical energy.

Heat transfer is the process of changing internal energy without doing work, while the internal energy of one body increases due to a decrease in the internal energy of another body. The energy transition comes from bodies with more high temperature to bodies with a lower temperature. There are its options: thermal conductivity, convection and radiation.
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Internal energy is not a constant value. It may change. If you increase the temperature of a body, its internal energy will increase (the average speed of movement of molecules will increase). As the temperature decreases, the internal energy of the body decreases.

Let's consider experience.
Let's attach a brass tube with thin walls to the stand. Fill the tube with ether and close it with a stopper. We tie it with a rope and begin to intensively move the rope to the sides. After a while, the ether will boil, and the force of the steam will push out the plug. The internal energy of the substance (ether) increased: it changed its temperature, boiling. The increase in internal energy occurred due to the work being done.

Heating of bodies can also occur during impacts, flexion or extension, or deformation. The internal energy of the body increases.

The internal energy of the body can be increased by doing work on the body. If the work is performed by the body itself, its internal energy decreases.

Let's consider experience.
We pump air into a glass vessel that has thick walls and is closed with a stopper through a specially made hole in it.

After some time, the cork will fly out of the vessel. At the moment when the stopper flies out of the vessel, we can see the formation of fog. Its formation means that the air in the vessel has become cold. The compressed air that is in the vessel does a certain amount of work when pushing the plug out. He performs this work due to his internal energy, which is reduced. Conclusions about the decrease in internal energy can be drawn based on the cooling of the air in the vessel. Thus, the internal energy of the body can be changed by performing certain work.

However, internal energy can be changed in another way, without doing work.

Let's look at an example.
The water in the kettle, which is standing on the stove, is boiling. The air, as well as other objects in the room, are heated by a central radiator. In such cases, the internal energy increases, because body temperature increases. But the work is not done. This means that a change in internal energy may not occur due to the performance of certain work.

Let's look at an example.
Place a metal knitting needle in a glass of water. The kinetic energy of hot water molecules is greater than the kinetic energy of cold metal particles. The hot water molecules will transfer some of their kinetic energy to the cold metal particles. Thus, the energy of the water molecules will decrease in a certain way, while the energy of the metal particles will increase. The water temperature will drop, and the temperature of the knitting needle will slowly increase. In the future, the difference between the temperature of the knitting needle and the water will disappear. Due to this experience, we saw a change in the internal energy of various bodies. We conclude: the internal energy of various bodies changes due to heat transfer.

The process of converting internal energy without performing a certain work on the body or the body itself is called heat transfer.

We found out that evaporation of a liquid is possible only if there is a flow of heat to the evaporating liquid. Why is this so?

Firstly, during evaporation the internal energy of a substance increases. The internal energy of saturated vapor is always greater than the internal energy of the liquid from which this vapor was formed. The increase in the internal energy of a substance during evaporation without a change in temperature occurs mainly due to the fact that when it passes into vapor, the average distance between the molecules increases. At the same time, their mutual potential energy increases, since in order to move molecules apart over long distances, work must be expended to overcome the forces of attraction of molecules to each other.

In addition, work is done against external pressure, because steam occupies a larger volume than the liquid from which it was formed. The work done during vaporization becomes especially clear if we imagine that the liquid is evaporating in a cylinder and that the resulting steam is lifted by a light piston (Fig. 492), while doing work against atmospheric pressure. This work is easy to calculate. Let's do this calculation for water boiling at normal pressure and, therefore, at temperature. Let the piston have area . Because it's normal atmospheric pressure equal, then a force acts on the piston. If the piston rises by , work will be done. This creates pair. The vapor density at is equal to , so the vapor mass is equal to . Consequently, when steam is formed, work against external pressure will be spent .

Rice. 492. The resulting vapors lift the piston. In this case, work is done against external pressure forces

When water evaporates, (specific heat of evaporation) is consumed. Of these, as our calculation shows, they are spent on working against external pressure. Therefore, the remainder equal to represents the increase in the internal energy of steam compared to the energy of water. As you can see, for water, most of the heat during evaporation goes to increase internal energy and only a small part is spent on performing external work.

297.1. Determine the increase in internal energy during the evaporation of alcohol, if it is known that the vapor density of alcohol at the boiling point is equal to .