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The law of conservation of energy is one of the important laws in Physics. The article below Nguyễn Tất Thành will accurately answer the questions: Whose law of conservation of energy is it? What is the law of conservation of energy? As well as providing statements of the law of conservation of energy, which can help readers consolidate their knowledge and apply it well to related questions.

What is energy?

Energy is the characteristic of any object’s ability to do work. The index of this energy is related to the movement of particles and the magnetic field. The energy and mass of an object are related to each other based on the theory of relativity.

In Physics, energy is considered a conserved quantity. The law of conservation of energy tells us that energy is neither naturally created nor naturally destroyed by anyone.

Organisms on Earth all need energy to live, such as humans get energy through food. Current civilization requires energy to operate, it gets energy from sources such as fossil fuel, nuclear or renewable,…

The basis for forming the law of conservation of energy

To know what is the law of conservation and conversion of energy? We will rely on the following foundations:

1. Convert potential energy into kinetic energy and vice versa. Loss of mechanical energy

People saw the transformation from potential energy to kinetic energy and vice versa before the law of conservation was known. In natural phenomena, we will see a clear transformation between potential energy and kinetic energy. Mechanical energy will be converted into potential energy thanks to the parts lost in mechanical energy and it can be said that mechanical energy always decreases.

2. Convert mechanical energy into electrical energy and vice versa. Loss of mechanical energy

In the case of loss based on the law of conservation of mechanical energy, it occurs when mechanical energy is converted into electrical energy and vice versa. In most electric motors today, we see that electrical energy is converted into mechanical energy. As for generators, on the contrary, most mechanical energy will be converted into electricity.

If mechanical energy is increased compared to the original, we can see that it is other energy that has been transformed into it.

State the law of conservation of energy

In Chemistry and Physics, this law is understood: “The total energy of an isolated system is always constant and means it will be conserved over time”.

From there we can state the specific law of conservation of energy as follows:

“Energy will not be naturally created or destroyed, but will change from one form to another or from one object to another.”

These explanations can be similar to the explanation of why an object’s mechanical energy increases or decreases. In addition, it also explains why objects cool or heat up. All are based on the transformation of energy in natural thermal, mechanical or electrical phenomena. In addition, they also confirm that the transformation of objects is based on the law of conservation.

For example:

Drop a marble into the bowl. At this time, the marble’s energy is gravitational potential energy. When the marble falls into the cup, it moves around the cup for a period of time and will now have kinetic energy. At the same time, when it falls, it also makes noise, which is acoustic energy. In addition, when the marble falls, it will move causing friction with the cup surface, generating heat energy.

Thus, when the marble is dropped into the bowl, not only does it have one initial form of energy, potential energy, but the marble is transformed into at least three new forms of energy: kinetic energy, negative energy, and heat energy.

Who discovered the law of conservation of energy?

The law of conservation of energy is a research process carried out by many scientists and Émilie Du Châtelet was the first to propose and test it.

After the birth of mechanics in 1826, James Prescott Joule demonstrated the conversion of energy from functional energy to thermal energy in 1854. Until 1981, Julius Robert Mayer – a German Physicist had statements about energy conservation.

Although many researchers found and proved it correctly, the Physics world only recognized Julius Robert Mayer as the author of the law of conservation of energy.

Conservation of energy in mechanical oscillations

In fact, the energy in mechanical vibration is called mechanical energy, which is equal to the sum of kinetic energy and potential energy according to a closed system of constant mechanical energy. So:

What is kinetic energy?

Kinetic energy is the form of energy created from its motion. When an object has kinetic energy, that object can exert force on another object and do work.

Formula to calculate the kinetic energy of a free falling object:

In there:

• Wd: Is the kinetic energy of the object (J)

• m: Is the mass of the object (kg)

• v: Is the speed of the object (m/s)

What is potential energy?

Potential energy is a quantity in Physics, representing an object’s ability to do work and it exists in the form of energy.

Formula for calculating the potential energy of a freely falling object:

In there:

• Wt: Is the potential energy of the object (J)

• m: Is the weight of the object (kg)

• H: Is the height of the object when freely falling (m)

Expression for conservation of mechanical energy

The mechanical energy of an object is a conserved quantity when moving in gravity only under the influence of gravity.

In there:

• Wd1: Is the kinetic energy of an object at a position with speed v1

• Wd2: Is the kinetic energy of an object at a position with velocity v2

• Wt1: Is the potential energy of the object at height h1

• Wt2: Is the potential energy of the object at height h2

Based on the above expression we see that:

When an object is in free fall, the kinetic energy will be zero if the potential energy reaches its maximum. Potential energy is zero when kinetic energy reaches its maximum. As potential energy increases, kinetic energy will decrease, but the sum of potential energy and kinetic energy is a constant quantity.

See more: What is the formula for adding velocity? How to apply (Grade 10 Physics Answers)

Formulas related to the law of conservation of energy

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After knowing whose law of conservation of energy? As well as the concept of this law, below are some related formulas and exercises for you to practice:

Formula to calculate Work

In there:

• A: Work of force F (unit is J)

• F: Force acting on the object (unit is N)

• S: Distance the object moves (unit is m)

• The unit of work is the joule (symbol J).

1J = 1N.1m = 1Nm

1 kJ = 1000 J

Multiples of joules are kilojoules (kJ)

Average capacity

In there:

• P: Power (unit is J/s or W)

• A: Work done (unit is Nm or J)

• t: Work execution time (unit is s)

1KW = 1000W; 1MW = 1,000,000W

Instant capacity

Contact expressions

Kinetic energy:

Relationship between kinetic energy and work:

Gravitational potential energy:

Relationship between gravitational potential energy and work:

Work of gravity (fall):

Elastic potential energy

Relationship between elastic potential energy and work:

Function:

Law of conservation of mechanical energy:

The kinetic energy height is n times the potential energy:

Efficiency:

In there

• Aci: Work is useful
• Atp: Total work

Some exercises illustrate the law of conservation of energy

After understanding the theory of energy conservation, below are some related exercises for you to practice together:

Some practical exercises on energy conservation to practice by yourself

I: Multiple choice section

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Lesson 1: In natural phenomena, there is often variation between:

A. Electrical energy and potential energy

B. Potential energy and kinetic energy

C. Optical energy and kinetic energy

D. Chemical energy and electrical energy

Lesson 2: In the process of converting potential energy into kinetic energy and vice versa in natural phenomena. Mechanical energy always decreases, the lost mechanical energy is converted into:

A. Thermal energy

B. Chemical energy

C. Optical energy

D. Nuclear energy

Lesson 3: In an electric motor, most electrical energy is converted into:

A. Electricity

B. Chemical energy

C. Optical energy

D. Mechanical function

Exercise 4: Choose the correct statement.

A. In an electric motor, most of the electrical energy is converted into heat energy.

B. In generators, most mechanical energy is converted into chemical energy.

C. The final useful energy obtained is always greater than the initial energy supplied to the machine.

D. The energy lost is converted into another form of energy.

Lesson 5: Which of the following statements is correct regarding the law of conservation of energy?

A. Energy can be created or destroyed, converted from one form to another or transferred from one object to another.

B. Energy cannot be created or destroyed but can be transferred from one object to another

C. Energy is not created or destroyed, but only converted from one form to another or transferred from one object to another.

D. Energy is not created or destroyed but only converted from one form to another

Lesson 6: In a generator, the collected electrical energy is always smaller than the mechanical energy supplied to the machine. Why?

A. Because a unit of electrical energy is larger than a unit of mechanical energy

B. Because part of the mechanical energy has turned into a form of energy other than electricity

C. Because part of the functional energy has disappeared on its own

D. Because the quality of electrical energy is higher than the quality of mechanical energy

Lesson 7: In the processes of converting kinetic energy to potential energy and vice versa, what always happens to mechanical energy?

A. Always preserved

B. Always increase

C. Always at a loss

D. Sometimes it increases, sometimes it decreases

Lesson 8: Solar cell efficiency is 10%. This means: If the battery receives:

A. 100J of electrical energy will produce 10J of light energy

B. 100J of solar energy will produce 10J of electricity

C. 10J of electrical energy will produce 100J of light energy

D. 10J of solar energy will produce 100J of electricity

Lesson 9: Say the efficiency of an electric motor is 97%. This means that 97% of the electricity used is converted into:

A. mechanical function

B. thermal energy

C. mechanical energy and thermal energy

D. mechanical energy and other energy

Lesson 10: Which of the following phenomena does not obey the law of conservation of energy?

A. The stove cools down when the heat is turned off

B. The vehicle stops when the engine is turned off

C. The iron cools down when the power is turned off

D. There are no phenomena

II: Essay part

Thus, through this article we have a better understanding of what the law of conservation of energy is, whose law of conservation of energy is and the formulas related to the law of conservation of energy. Hopefully this information will help you master and review the knowledge you have just learned in the most complete and best way. Please follow the basic knowledge section to learn more interesting information about the subjects!

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