Law of Conservation of Energy – What is eternal? If you look at the Big Indonesian Dictionary (KBBI), the word “eternal” can mean eternal , alias does not change . This conservation can also be part of Physics material, to be precise in the Law of the Conservation of Energy. Sinaumed’s must already know what kind of energy exists on this earth? There is kinetic energy, potential energy, heat energy, mechanical energy, and many more.
Well, if examined based on the Law of the Conservation of Energy, it can mean that this energy can be eternal all the time, with the same value both before something happens and after. Then, what is the Law of the Conservation of Energy in terms of Physics? What types of Law of Conservation of Energy exist on this earth? Who invented the Law of the Conservation of Energy so that it can be applied by today’s technology? So that Sinaumed’s understands these things, let’s look at the following review!
Understanding the Law of Conservation of Energy
Basically, the law of the conservation of energy is one of the laws of Physics which states that energy is eternal, aka eternal, so it can’t change all the time, and has the same value both before something happens and after. Well, the existence of this energy can also be changed in form with a magnitude that will always be the same. In this law of conservation of energy, the energy in question is kinetic energy, potential energy, mechanical energy, and others.
The law of the conservation of energy was discovered by a British physicist, James Prescott Joule, which reads: “Energy can neither be created nor destroyed, but can be transferred from one form to another….” . That is, an energy involved in chemical and physical processes can experience transfer or change of form. Example: radiant energy can be converted into heat energy, potential energy can be converted into electrical energy, chemical energy can be converted into electrical energy.
Here’s a little trivia , apart from being eternal or eternal, the existence of energy has several characteristics, namely:
- Energy transformation, meaning that energy can be converted into other forms.
- Energy transfer, meaning that heat energy can be transferred from one material to another.
- Energy can be transferred to other objects, especially through a force that causes a shift, that is what is called mechanical energy.
- The energy is permanent alias immortal, but it can neither be created nor destroyed.
The Law of the Conservation of Energy Formula
As with other physical laws, the Law of the Conservation of Energy also has its own formula, namely:
Em1 = Em2
Ek1 + Ep1 = Ek2 + Ep2
Em1 = initial mechanical energy
Em2 = final mechanical energy (J)
Ek1 = initial kinetic energy
Ek2 = final kinetic energy (J)
Ep1 = initial potential energy
Ep2 = final potential energy (J)
Problems and Discussion Regarding the Law of Conservation of Energy
Example Question 1
Yuyun dropped a motorbike key from a height of 2 meters so that the moving key fell freely under the house. If the acceleration due to gravity is 10 m/s 2 , then the speed of the key after moving 0.5 meters from its initial position is
h1 = 2 m, v1 = 0, g = 10 m/s2, h = 0,5 m, h2 = 2 – 0, 5 = 1,5 m
v2 = ?
Based on the law of conservation of mechanical energy
Em1 = Em2
Ep1 + Ek1 = Ep2 + Ek2
m.g.h1 + ½ m.v12 = m.g.h2 + ½m.v22
m. 10 (2) + 0 = m. 10 (1,5) + ½m.v22
20 m = 15 m + ½m.v22
20= 15 + ½ v22
20 – 15 = ½ v22
5 = ½ v22
10 = v22
v2 = √10 m/s
Example Problem 2
A block slides from the top of a smooth inclined plane to the bottom of the inclined plane. If the top of the inclined plane is at a height of 32 meters above the floor, then the speed of the block when it arrives at the bottom of the plane is
h 1 = 32 m, v 1 = 0, h 2 = 0, g=10 m/s 2
v 2 = ?
Types of Laws of Conservation of Energy
Since earlier, we have always discussed energy, what exactly is energy? According to Harjono (2007), energy is the ability to do work. An object will be said to have energy if the object produces a force that can do work. Meanwhile, according to Purwanti (2005), an object can be said to have energy if the object can produce something (through force) that can do work.
In International Units (SI), the amount of energy is expressed in units of Joules (J). One joule is equal to 1 Newton Meter (1 J = 1 Nm). Well, in the Law of the Conservation of Energy there are several types, namely:
1. Kinetic Energy
An object that moves tends to have the ability to do business, if so then the object can be said to have energy. The energy in moving objects is called kinetic energy. For example: a stone thrown can break glass.
To calculate the presence of kinetic energy contained in an object, it can be obtained by connecting the GLB equation (Regular Straight Motion) with the GLBB equation (Regularly Changing Straight Motion) for the initial velocity (v0) = 0 m/s. This kinetic energy can be calculated using the following formula:
m = Mass of object (kg)
v = object speed (m/s)
I = Energy kinetic (Joule)
2. Potential Energy
Potential energy is the energy possessed by an object because of its location or position from a certain reference. That is, this potential energy is energy that is indeed produced by forces that depend on the position of an object in relation to its environment. One of the most common potential energies encountered in everyday life is gravitational potential energy.
What is gravitational potential energy? Gravitational potential energy is the energy possessed by an object due to its height relative to a certain reference plane. The higher the position of an object from the reference field, the greater the gravitational potential energy it has. For example: coconuts on a tree have gravitational potential energy, which if they fall and hit the tile, it can produce an effort in the form of breaking the tile.
Mathematically, this potential energy can be formulated as follows:
3. Mechanical Energy
In the nature of energy previously described, there is one property which states that energy cannot be created or destroyed. However, this energy can change from one energy to another. Well, energy that can be transferred to other objects, especially through a force that causes a shift, is called mechanical energy.
The law of conservation of mechanical energy states that “the sum of potential energy and kinetic energy at any point in a gravitational field is always the same…”. In addition, the law of the conservation of mechanical energy will also apply if we ignore friction or other non-conservative forces, or if only conservative forces act on an object. Usually, mechanical energy will be associated with the sum of potential energy and kinetic energy, resulting in a formula equation in the form of:
Please note that this conservative force is a force that can produce a two-way change, namely between kinetic energy and potential energy. Examples of conservative forces are gravitational forces and spring forces. Now, if only conservative forces act on an object, then the total mechanical energy will neither decrease nor increase (in this case it means that the total mechanical energy will be constant).
If kinetic energy increases, then potential energy must decrease by the same amount in order to compensate. Thus, the total potential energy plus kinetic energy, the result will remain constant. That is what is called the principle of conservation of mechanical energy for conservative forces.
Examples of Application of the Law of Conservation of Energy
The existence of the law of the conservation of energy is not merely a formula, but can also be applied in everyday life. Even without Sinaumed’s realizing it, the technologies around us are also the application of the law of the conservation of energy, you know… So here are some examples.
1. Musical Instruments
Does Sinaumed’s know that when we play a musical instrument, the law of the conservation of energy actually manifests? Yep, for example when using a guitar by plucking, it turns out that we are applying kinetic energy from the hand muscles, which the guitar then converts into sound energy.
Many musical instruments apply the law of conservation of energy, especially this kinetic energy, namely drums, piano, violin, and harp.
2. Heating Machine
There are various types of heating machines, from water heating kettles, soldering irons, irons, water heaters, toasters, to heating machines, which both apply the law of the conservation of energy. In contrast to musical instruments that use kinetic energy, heating machines tend to use potential energy, especially electric potential energy.
The electric potential energy is later converted by the heating element of the machine so that it can become heating energy.
3. Motorized Vehicles
Basically, all motorized vehicles in our lives, from cars, motorcycles, trucks, and others, use fossil fuels. Now in this case, the energy used is the chemical potential energy that comes from the fossil fuel, which is converted by the vehicle engine into kinetic energy so that it can move the vehicle. Therefore, without the chemical potential energy that comes from fossil fuels, motorized vehicles will not be able to run.
4. Hydro Power Plant
Due to the force of gravity on this earth, water will always flow from high places to lower places. The higher position of the water causes the potential energy to be greater. Through this, the power plant utilizes the potential energy of water, especially to rotate the electricity generator turbine. Later, the potential energy of the water will turn into kinetic energy which can turn turbines and generate electrical energy.
Get to Know the Inventor of the Law of Conservation of Energy
The existence of the law of the conservation of energy, which can be applied in today’s technology, clearly provides various benefits for everyday human life. All of these things cannot be separated from the thoughts of James Prescott Joule as the discoverer of the law of the conservation of energy. James Prescott Joule was born on December 24, 1818 and died on October 11, 1889 who was a British physicist. In terms of the law of the conservation of energy, he stated that “Energy can neither be created nor destroyed”. For his services, even the unit of energy was named Joule according to his name.
James Prescott Joule was the second son of five siblings. His father, Benjamin Joule, was a brewery entrepreneur. Therefore, James can be called a rich child, but unfortunately, since childhood he could not go to school like other children in general because he suffered from a spinal disorder. Since he didn’t go to school, his father also found a private teacher to teach James at school. Apart from that, James is also a quiet and shy person.
As the son of a rich businessman, James can do whatever he likes, one of which is reading books. Indeed since childhood, James has been interested in electricity that he even often conducts experiments to conduct electric currents in the human body! Although in a small capacity.
Benjamin Joule as his father, noticed that his second child really liked science, so that at the age of 16, James was sent to the University of Manchester. There, he attended some science training by John Dalton. Well, back from science training, his father again built a private laboratory for James underground. This was done so that James could freely conduct experiments to find the relationship between heat energy and electrical energy.
In 1840, James managed to publish a scientific work on the heat generated by electric currents. Then in 1843, James returned to publish the continuation of his scientific work on how to convert work into heat. He conducted experiments using pedal wheels. Finally, James formulated the concept of physics regarding the equivalence of mechanical energy and heat energy .
Four years later, James succeeded in formulating the law of the conservation of energy which became the first law of the laws of thermodynamics. The law states that energy cannot be created or destroyed, but can be changed from one form to another.
Then in 1847 James met Lord Kelvin or William Thomson at a science discussion event. Lord Kelvin was interested in James’ discoveries and the scientific works that had been published. He also invited James to work together. From this collaboration, a physics concept called the Joule-Thomson Effect was born . The Joule-Thomson effect has developed into a science that studies the properties of matter at very low temperatures. The science is called Cryogenics.