### Sounds, Concepts, Formulas and Examples of the Law of Conservation of Energy

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**Law of Conservation of Energy – Sounds, Concepts, Formulas and Examples – **In our daily life there are many types of energy. In addition to potential energy and kinetic energy in ordinary objects (macroscopic scale), there are also other forms of energy. There is electrical energy, thermal energy, electrical energy, chemical energy stored in food and fuel, nuclear energy, etc. After the atomic theory emerged, it was said that other forms of energy (electrical energy, chemical energy, etc.) were kinetic energy or potential energy at the atomic level.

This energy can change from one form of energy to another. For example, when you turn on a neon light, at the same time, electrical energy is converted into light energy. Another example is the change of electrical energy into heat energy (iron), electrical energy into motion energy (fan) etc. The process of changing the form of energy is actually caused by a change in energy between potential energy and kinetic energy at the atomic level. At the macroscopic level, we can also find so many examples of energy changes.

Energy changes usually involve the transfer of energy from one object to another. The water in the dam has potential energy and turns into kinetic energy when the water falls. This kinetic energy is transferred to the turbine. The turbine motion energy is then converted into electrical energy. The potential energy stored in the stretched catapult can be transformed into the kinetic energy of the rock when the catapult is released. A curved arc also has potential energy. The potential energy of a curved bow can be converted into the kinetic energy of the arrow.

The example mentioned above shows that the transfer of energy is always accompanied by work. Water does work on turbines, rubber slingshots do work on rocks, bows do work on arrows. This means that work is always done when energy is transferred from one object to another

## The Law of Conservation of Energy reads

*“Energy can neither be created nor destroyed, but can be transferred from one form to another”*

The remarkable thing in physics and in our daily lives is that when energy is transferred or converted from one form to another, it turns out that no energy is lost or lost in any of these processes. this is the law of conservation of energy, an important principle in physics. The law of conservation of energy can also be stated as follows:

* “Energy can be changed from one form to another and transferred from one object to another but the amount is always constant. So the total energy neither decreases nor increases.*“

The energy of the universe is constant, so the energy involved in a chemical and physical process is only a transfer or change of form of energy.

**Examples of energy changes:**

- Radiant energy is converted into heat energy.
- Potential energy is converted into electrical energy.
- Chemical energy into electrical energy.

## Law of Conservation of Mechanical Energy

An object thrown upwards will have potential energy and kinetic energy. Potential energy is due to its height, while kinetic energy is due to its motion. The higher the object is thrown upwards, the greater the potential energy. However, the smaller the kinetic energy. At maximum height, an object has the highest potential energy and the lowest kinetic energy.

To better understand kinetic energy consider a ball thrown upwards. The speed of the ball that is thrown upwards decreases over time. The higher the position of the ball (the greater the gravitational potential energy), the smaller the velocity (the smaller the ball’s kinetic energy). When it reaches its highest state, the ball will be at rest.

This means that the gravitational potential energy is maximum, but the kinetic energy is minimal (v = 0). As the ball begins to fall, its velocity begins to increase (its kinetic energy increases) and its height decreases (the gravitational potential energy decreases). Based on the above incident, it seems that there is a kind of energy exchange between kinetic energy and gravitational potential energy. Does the law of conservation of mechanical energy apply in this case?

### Let’s analyze:

When an object falls, its height decreases, its potential energy decreases, while its kinetic energy increases. When an object reaches its lowest point, its potential energy is smallest and its kinetic energy is greatest. Why is that?

Ball that falls from a height *h*. Consider the picture above, when a ball is at a height h, then the potential energy at point A is

*E _{pA} = m · g · h*, while the kinetic energy

*E _{kA} *= mv

^{2}

Because *v = 0*, then *E _{kA} *=

*0*. The sum of the potential energy at point A and the kinetic energy at point A is equal to the mechanical energy. The amount of mechanical energy is:

*E _{mA} = E_{pA} + E_{kA}*

*E*

_{mA}= mgh + 0*E*

_{mA}= mghFor example, in time *t* second the ball falls how far *h*_{1} (point B), so the distance of the ball from the ground is *h – h*_{1}. The potential energy of the ball at point B is *E _{pB} = mg(h – h_{1}).* From point A to point B, the potential energy decreases by berkurang

*mgh*. Meanwhile, the kinetic energy when the ball is at B is as follows. When the ball falls as high

_{1}*h*, the ball is moving uniformly with an initial velocity of zero.

_{1}#### The object’s velocity is:

*v = v _{o} + g · t (v_{o} = 0)*

So, the kinetic energy of the ball at point B is:

The sum of the kinetic and potential energies after the object has fallen a distance h_{1} (at point B) is as follows.

*E _{mB} = E_{kB} + E_{pB}*

*E*

_{mB}= mgh_{1}+ (mgh*–*

*mgh*

_{1})*E*

_{mB}= mghSo, the mechanical energy at point B is *E _{mB} = mgh*

Based on the calculations, it shows that the mechanical energy at point A is the same as the mechanical energy at point *B (E _{mA} = E_{mB})*. So, it can be concluded that the amount of mechanical energy of an object affected by the gravitational force is constant.

If at the position at A the sum of the potential energy and kinetic energy is *E _{pA} + E_{kA}*, while at the position at B the sum of the potential energy and kinetic energy is

*E*, then:

_{pB}+ E_{kB}*E*or

_{pA}+ E_{kA}= E_{pB}+ E_{kB}*E*= fixed. This is called the law of conservation of mechanical energy.

_{p}+ E_{k}