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4.7. The law of conservation and transformation of energy

Lecture



Consider the process of changing the state of the body raised to a height h. Moreover, its potential energy

4.7.  The law of conservation and transformation of energy

The body began to fall freely 4.7.  The law of conservation and transformation of energy . It is known from kinematics that when it reaches the surface of the earth it will have a speed 4.7.  The law of conservation and transformation of energy ikinetic energy:

4.7.  The law of conservation and transformation of energy

The kinetic energy of a body that fell from a height h turned out to be equal to its potential energy, which it had before the fall. Consequently:

4.7.  The law of conservation and transformation of energy

On the surface of the earth h = 0 and potential energy 4.7.  The law of conservation and transformation of energy , but 4.7.  The law of conservation and transformation of energy is maximum. At the beginning of the fall 4.7.  The law of conservation and transformation of energy , but 4.7.  The law of conservation and transformation of energy those. potential energy is converted (converted) into kinetic. Thus, when a body falls in a body-to-earth system, the kinetic energy increases and, consequently, its change 4.7.  The law of conservation and transformation of energy equal to work 4.7.  The law of conservation and transformation of energy , has a positive sign, i.e.

4.7.  The law of conservation and transformation of energy (4.12)

The potential energy decreases, and, consequently, its change has a minus sign. Therefore, we can write:

4.7.  The law of conservation and transformation of energy (4.13)

Adding (4.12) and (4.13), we get

4.7.  The law of conservation and transformation of energy

or 4.7.  The law of conservation and transformation of energy

Amount 4.7.  The law of conservation and transformation of energy represents the total energy and therefore

4.7.  The law of conservation and transformation of energy , but

4.7.  The law of conservation and transformation of energy (4.14)

Thus, the energy of a closed conservative system remains constant for all processes and transformations occurring in it. Energy can transfer from one species to another (mechanical, thermal, etc.), but its total amount remains constant. This provision is called the law of conservation and transformation of energy.


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Physical foundations of mechanics

Terms: Physical foundations of mechanics