Conventional Energy
What Is The Law Of Conservation of Energy?

What Is The Law Of Conservation of Energy?

What Is The Law Of Conservation of Energy?

The simplest and most common explanation of energy conservation is, energy cannot be created nor destroyed. Although this does apply and is valid it is not as simple as it seems. Unfortunately, physics is not as straightforward as mathematics meaning, there are circumstances in which energy is not always conserved. The law of conservation of energy states that energy is constant in a system. Constant energy means energy is neither gained or lost. An isolated system is a closed space which is encompassed by the outside environment. An example of this closed space can be a battery, an engine, house or even neighborhood. The environment is everything outside of the closed space. Inside an isolated system energy is constant, many wonder how an engine can work if the energy is constant. The process is explained by the transfer of energy, rather than energy beginning in one form and continuing in that form throughout the systems entirety.

Different Forms of Energy

Energy can be found in many different kinds of forms the most basic are gravitational energy and kinetic energy. First one of the most common types of energy we all experience is gravitational potential energy. This is what pulls you down when you reach the peak of your jump. Gravitational energy is calculated with the mass of the object which is constant, gravity which is relatively constant and height. These values are proportional to gravitational energy with the value of gravity changing depending on how far you are from the earth core or if you’re on earth, to begin with. To simplify the concept of gravity being referred to as constant, small variations of radius from an object to the earth core slightly affect gravity. Gravity does have a noticeable variation from on earth’s surface and from outside the earth’s atmosphere. When dealing with a system on earth’s surface or near earth’s surface a value of 9.8m/s^2 is given to gravity.

Energy Explained

Gravitational energy is a very prevalent form of energy we experience daily, but it couldn’t exist without kinetic energy. Kinetic energy is how an object rises up or moves. An example of this is jumping requiring kinetic energy to perform the action and gravitational energy which pulls you back to the ground. Kinetic energy is made up of half of the object’s mass and half of the object’s velocity squared. These values are directly proportional to kinetic energy. Clearly, kinetic energy and gravitational energy are constantly working together, so much so that their combination is referred to as mechanical energy.

Mechanical Energy

Mechanical Energy is a very basic concept of the transfer of energy. A basic example of this is a person jumping up and down. As mentioned earlier the law of conservation of energy occurs in an isolated system, in this example, the isolated system is the earth and person. Why is the system so large? This is because without the earth in the system there will be no gravitational energy. As the person begins the jump all of the energy is in the form of kinetic energy and as the person rises some kinetic energy is transferred to gravitational energy. This continues until the person reaches the peak of the jump where their velocity is zero for a fraction of a second and the kinetic energy is zero. At the peak, the gravitational energy is at its max. As the person falls the energy is transferred to kinetic energy once again until the person reaches the ground.


Mechanical energy is a form of simple everyday energy transfer experienced by everyone constantly, however it is not as accurate to real life as one may think. Physics on paper is much more simplified than the actual real world physics we experience every second of the day. A huge misconception most have, especially in energy, is the law itself. Energy is theoretically neither lost or gained and kept constant in an isolated system, but this rule does not necessarily hold up in the real world. For example, you cannot accurately measure the kinetic energy of a train with just the values of velocity and mass, it will only provide an approximation. Friction is a force which makes energy much more complicated in real life. Prior understanding how fiction affects energy is important to understand friction in itself.

The Versatility of Physics

Prior concepts such as mechanical energy and gravity are what makes the conservation of energy laws. Most, when referring to energy only focus on gravity and kinetic energy this is a major mistake. Gravity and Kinetic Energy are important but are very simple. When dealing with physics simpler usually leads to more theoretical conclusions while more detailed terms and concepts are similar to real world situations. This can be easily shown using the motion of a car. In simple terms, the car is experiencing kinetic energy and friction to propel it forward and gravity cancels out the normal force. A more detailed explanation in physics terms uses the grade of the surface the car is on, friction on all four wheels, rotational energy, the kinetic energy of the car, normal force and gravity. Although many values may be minute, the inclusion of them provides a realistic answer which can be applied in the real world. The law of conservation of energy states energy is neither created nor destroyed in an isolated system. Fortunately, more detailed scenarios are not exempt from this rule, this means that they can be solved, but require more work. This is an advantage of physics, scenarios can be simplified for theoretical reasons, but more detail means these same concepts can be used in real world scenarios. Physics can be used to explain many of the events we face on a daily basis. From a subway train, to a busy bridge, these all use physics concepts such as the law of conservation of energy to exist. Theoretical scenarios are used to understand them while detailed evaluations are used to build them.

Friction Misconceptions

There are two very common misconceptions about friction. One being that objects in free fall don’t experience friction. This is understandable due to the effortless movement we experience through the air. However, it is wrong and we experience the effects of air friction daily. Air friction is how birds fly, without the ability to push air down and behind them, they would not be able to take off let alone soar. Another quick example of this is a bird feather floating slowly down to the ground as opposed to a bowling ball being dropped from the same height. Theoretically, these objects should reach the ground at the time because they are both accelerating at the same value of 9.8m/s^2. However, this is clearly not the case. The feather is much more affected by the air friction because it is being pushed up and back because of its light weight and large surface area. The bowling ball, on the other hand, is dense and heavy so air friction barely slows it down especially from shortfalls. Another common misconception about friction is which one a car experiences. And yes a car does experience friction even though, it has wheels. Most typical drivers those who exclusively use their cars as a means of travel rather than for travel and pleasure might make the obvious assumption. The obvious assumption that static friction holds the car in place when parked or when on the breaks, and kinetic friction moves the car. This assumption is wrong, static friction is the force which not only keeps the vehicle in place but propels it forwards. This is because as the tire spins it makes contacts with the ground but on different locations of the tire. What’s happening is the tire grips the road and pushes forwards and grips the roads again a continuous process only a wheel can produce. However, kinetic energy is experienced by vehicles in certain conditions. A skidding wheel, burnout and wheel spin in first gear are all examples of kinetic friction. This is because the two surfaces are sliding past each other failing to grip and in turn failing to propel the vehicle forward.

 Friction vs Energy

So how does friction affect energy? It affects energy in many different ways including a different theorem, the work-energy theorem. The work-energy theorem combines work and energy allowing the ability to find values with the information provided. The theorem is unique because once friction is introduced to the system we can use it. The work-energy theorem is composed of the sum of the change of energies whether it be gravitational, kinetic and compulsory friction which is equal to external work. This is where energy transformation becomes interesting and more practical. The presence of friction is significant and referred to as thermal energy. Energy is transferred to thermal energy leaving small amounts of heat in the isolated system. External work is zero in an isolated system however, this equation can be done with a value of external work. The work-energy theorem allows for a physicist to find values of different kinds of energies in an isolated system or a system with an external force acting on it.

E=mc 2

All the prior information is very important to understanding energy, but more often than none those who don’t understand physics will usually refer to Albert Einstein’s Theories when referring to energy. Albert Einstein’s theory states that Energy is equal to the product of mass and speed of light in a vacuum squared. Energy experienced by usual people on a day to day basis is under the umbrella of the law of conservation. It deals with straightforward simple energy such as gravity, kinetic energy, thermal energy, rotational energy and so on. Most can see the importance of the various energies and the laws that accompany them. Albert Einstein’s form of energy he is referring to in his theorems is a different kind of energy. Nuclear fission is the kind of energy Einstein refers to. Nuclear fission is not a complicated physics concept, but it does deserve an explanation. Many forms of energy such as the burning of coal and gasoline are done by combing molecules with other molecules, this can be done with combustion. A chemist explanation is that the valence electrons moving from molecule to molecule are used to provide energy. Although this works to provide adequate energy, there is plenty of energy lost throughout this process. Nuclear fission is a much stronger way to produce energy. It involves splitting the nucleus of molecules to obtain the energy in the nucleus. This is done today with nuclear energy and on the sun’s surface. Nuclear energy is produced by splitting the nucleus of nuclear atoms. This produces great amounts which are used to produce energy.

Real World Energy

With this information, it is easy to confirm which one of the equations are more practical to everyday use. The common misconception is that you can calculate any kind of energy with Einstein’s theorem. Unfortunately, this is not the case and many can show their lack of knowledge in science when they immediately refer to this equation. The most common mistake made by many people is simply thinking that science is easy. Physics, chemistry, thermodynamics and the many other branches of science are in no way possible easy. The overwhelming amount who claim they are knowledgeable by simply stating Einstein’s equation are more than likely the least knowledgeable in physics and it’s counterparts. This is because science requires the full understanding of all the concepts and theories in order to properly use or repeat any information found or observed. No step can be skipped, no concept can be solely learned and no human is all knowing of physics as there is no limit to the knowledge that can be obtained and learn. A simple way to confirm that you or someone else knows what they’re talking about when it comes to physics is by asking of the concepts. Yes acceleration is calculated by change in velocity divided by time, but what does acceleration mean.

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  1. Quotes Tadka

    January 24, 2017 at 5:09 pm

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