Object A does work on object B, the energy in A decreases, and the temperature decreases

Object A does work on object B, the energy in A decreases, and the temperature decreases, so why don't you see your hand cool down when you do work on other objects? When the human body does work on objects, how can the body feel the heat instead?

This thing, only when object A uses internal energy to do work on object B, the temperature will decrease, it is very difficult to do work in the form of internal energy, generally only heat engines can do it (for example, internal combustion engines, steam engines, ramjet engines and jet engines, people definitely don't have this ability, creatures will not have such a powerful condition, the conditions for them to do work are generally at high temperatures), the hand is converted into mechanical energy to do work on other objects with chemical energy, and the hand will definitely not be cold, Due to the heat loss of chemical energy (chemical energy generally cannot be 100% converted into machinery, and the conversion rate of chemical energy internal energy cannot reach 100%), chemical energy is partially converted into mechanical energy, partly into internal energy, and partly without conversion, so there will be heat loss, which will increase the temperature of the muscles, and then there will be friction on the contact surface of the work, so that the mechanical energy will eventually be converted into internal energy, so that the temperature of the part that does the work (such as the hand, the body, and not the muscles) will rise. It can be seen that there are two ** temperature increases, one is friction and the other is chemical energy loss. You can try to keep pushing the wall with a lot of force, your hand won't move, so there's no friction, but soon you find that your body muscles are hot, which is the burning of chemical energy, which can't be converted into mechanical energy due to resistance.

There are many more such examples. For example, if the resistance of the motor is very small, then the motor will heat up for a long time, and if the resistance of the motor is large, then the motor will be very hot all at once. This is a matter of converting electrical energy into mechanical energy, and the conversion rate of mechanical energy is very low when the resistance is high.

When the motor is energized and stuck, the temperature rises very quickly. It's the same as pushing a wall with chemical energy from an energy point of view.

When the human body does work on objects, the total energy of the person will inevitably decrease. (This is an immutable truth, Newton's classical physics, which is no longer applicable when it comes to high-velocity microscopic speeds.) But so far I haven't found anything that doesn't apply. ）

The total energy of the person is reduced, why is the body hot?

This is because when the human body does work, it consumes more of its own biological energy (which is converted from the chemical energy you eat), which can be converted not only into the object you are doing the work on, but also into your own internal energy. So your body will feel the heat. So the more you do, the more you have to eat in the next meal.

Your body is hot because of the heat generated by friction in your joints, muscles, etc.

Your own internal energy is reduced, and part of it is converted into heat energy and work on objects.

The reduction of internal energy and the reduction of temperature are only suitable for ideal gases.

While the hand does work on other objects, there is also the process of chemical energy and mechanical energy.

The human body does work on objects, and how the body feels heat instead is because of friction.

It looks physical, but it's actually a living thing.

Breathing, you know, breaks down organic matter and releases energy, which is partly in the form of heat.

Because glucose in the body breaks down and produces heat, body temperature is maintained. To do work on other objects, what is actually consumed is the energy in the body rather than the internal energy of the hand. When people do work on objects, they also consume glucose in the body, and glucose decomposes to produce water, carbon dioxide, and heat, so it feels hot again.

Frictional heat transfer though will eventually bring the two objects to the same temperature.

But man is an endothermic animal.

The temperature does not change.

The hand does work on other objects, converting part of the chemical energy in the human body into the mechanical energy of the object, and part of it into the internal energy of the person, that is, thermal energy.

a. After the object is exothermic, the internal energy decreases, but the temperature does not necessarily decrease, such as when the crystal solidifies, so A is wrong;

b. For objects with high temperatures, when the mass is small, the internal energy of the object is not necessarily large, so B is wrong;

c. After the object is heat-released, the internal energy decreases, and the temperature may remain unchanged or decrease, so C is correct;

d. The temperature of the object does not change, and the internal energy may decrease, such as when the crystal melts, the temperature does not change, but the internal energy increases, so D is wrong

Therefore, C

a. The object is exothermic, the internal energy is reduced, and the temperature is not necessarily reduced, such as water solidification, heat is released, and the internal energy is reduced, but the temperature remains unchanged, so A is wrong;

b. Because the magnitude of internal energy is related to mass, temperature and state, the object with large internal energy is not necessarily at high temperature, and may be caused by mass or state, so B is wrong;

c. Heat is transferred from a high-temperature object to a low-temperature object, so C is wrong;

d. The condition of heat transfer is that there is a temperature difference, so when two objects with different temperatures come into contact with each other, the transfer of internal energy will definitely occur, and the transfer of heat is correct

Therefore, choose D

a. After the object is heated, the internal energy is reduced, but the temperature does not necessarily decrease the judgment, such as when the crystal solidifies, so A is wrong;

b. For objects with high temperatures, when the mass is small, the internal energy of the object is not necessarily large, so B is wrong;

c. After the object is heat-released, the internal energy decreases, and the temperature may remain unchanged or decrease, so C is correct;

d. The temperature of the object does not change, and the internal energy may decrease, such as when the crystal melts, the temperature does not change, but the internal energy increases, so D is wrong

Therefore, C

The correct answer is: BAs the temperature of the object increases, the internal energy must increase aThe internal energy of the object increases, and the temperature must increase - the crystal can change within the melting point (or freezing point), but the temperature is constant;

c.When work is done on an object, the internal energy of the object must increase - the work done does not necessarily increase the internal energy, for example, the object is lifted to a certain height, and the lifting force does work on the object, but the internal energy of the object does not change;

d.The temperature of the object is high, and the internal energy is large - different substances, substances of different masses, the higher the temperature, the higher the internal energy.

The answer is A, B answer can also be Changsan doing work, C answer, 0° water is the internal energy of the car, D answer, to keep the temperature closed and equal, the energy required is related to the mass, so the internal energy is different.

When the temperature of an object decreases.

aThe object must have emitted heat.

b. The object must have done work externally.

c must have done work on the object.

dNone of the above statements are true.

The correct answer is: a

b and c: In winter, an object is placed at rest outside, its temperature decreases, the object does not do work on the outside, and the outside does not do work on the object, but the temperature decreases. So, b and c are wrong.

A: When the temperature drops, there is a heat exchange with the outside world. And it must have been heated, so the temperature went down.

Choose the D Kraberon equation PV=NRT

First, we idealize all the conditions and assume that the object is an ideal gas.

A: Wrong, as long as you build an adiabatic cylinder, as long as the system does external work, the temperature can drop, since the insulation, there is no such thing as exothermy.

d May emit heat or do work to the outside world.

Analysis of test question D: When the outside world does work on the object, if the object releases heat to the outside at the same time, the internal energy of the object may also decrease, so A is not true; The increase in the temperature of the object in b means that the average kinetic energy of the molecules in the object must increase, but it does not mean that the kinetic energy of all molecules increases, so b is also incorrect; In C, when the molecules are close to each other, if the distance between the original molecules is large, and the molecular force is positive when they are close, then the molecular potential energy will be reduced at this time, so C is not right; In D, in the process of the molecules moving away from each other, the gravitational force and the repulsion force of the molecules are reduced, but the repulsion force decreases more, and the external manifestation is the gravitational force of oneself, so D is correct.

The answer is d

A can do work, if an object is doing work, it can be said to have mechanical energy, but the question only says that it has the ability to do work.

b. If the length of the spring extension exceeds the elastic deformation range, the spring is no longer a spring.

cThere are two ways to change the temperature: work done and heat transfer.

d correct. Newton's laws can be known that when the equilibrium force is applied to the stationary or uniform motion, then the kinetic energy does not change.

A: False. Being able to do work means having potential energy, not mechanical energy;

B: False. The longer the spring is stretched within the elastic deformation, the greater the potential energy; Exceeding the elastic deformation range, the spring fails;

C: Absorb what? Doing work on an object can also increase its internal energy.

d correct. Is energy conserved?