How do I open my inner energy

Calculation of the internal energy

In this text we explain the concept of inner energy, how it is composed and how you can calculate it.

The internal energy describes the complete energy potential that a system has stored in itself. A body or a substance is understood as a system. In such a system, two different forms of energy meet, among other things. This is on the one hand the potential energy and on the other hand the kinetic energy. If you are still unfamiliar with these two forms of energy, you can read through these texts again.

Basics of energy

A very important aspect in the treatment of the forms of energy is the knowledge that energy cannot be generated or destroyed. Only the form of energy can be changed. Using an example, we would like to show you how this is to be understood exactly and what significance this has for the internal energy of a system.

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Potential energy is converted into kinetic energy when sliding

Change of forms of energy

As you can see in the graphic, the firefighter goes through various states during action, which can be illustrated with the different forms of energy. At the beginning he stands above the bar by means of which he wants to slide to his emergency vehicle. In this example, the firefighter is the system that has a certain energy potential. At this point the firefighter has a high potential energy ($ E_ {pot} $). Now he goes over to sliding on the pole towards the emergency room. That is, the system does work and in the process the potential energy is converted into another form. Due to gravity, the firefighter goes into a state of motion. The potential energy becomes kinetic energy ($ E_ {kin} $). During the slide, the potential energy decreases (as the altitude the system is at decreases) and the kinetic energy increases (due to the increase in the rate of fall). Once on the ground, the potential energy has the value zero, since the height also has the value $ h = 0 $. Since the firefighter has now also completed the process of sliding, the kinetic energy is also at the value zero. So the original energy potential of the potential energy seems to have disappeared. However, as you have already learned above, energy cannot go away. Accordingly, this must have changed to another form.

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Inner energy

If we look in more detail at the process of our firefighter sliding, we can see that there is another process going on. To regulate the speed of his fall, the firefighter brakes the fall with his hands on the bar. This warms his hands. At this point something happens to the existing energy. The potential resulting from the potential energy is not only converted into kinetic energy, but also into what is known as internal energy. In our example, this is illustrated by the heating of the system (this refers to the fireman’s hands). The sliding process creates a chain in which the forms of energy flow into one another. The potential energy becomes kinetic energy, which in turn (through braking) is converted into internal energy.

internal energy arises from potential and kinetic energy
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$ E_ {pot} \ rightarrow $$ E_ {kin} \ rightarrow $$ E_ {inn} $

Calculation of the internal energy

In summary, you can remember that the potential energy is first converted into kinetic energy and then into the internal energy, which is finally stored in the system. To calculate the internal energy in our example, you have to calculate the potential energy of the fireman initially available using the formula $ E_ {pot} = {m} \ cdot {g} \ cdot {h} $ to calculate. For this you need the mass of the body or the system ($ m $), the constant acceleration due to gravity $ {9.81} \ frac {m} {s ^ 2} $ and the height ($ h $) at which the System is located. For an 80 kg firefighter who was at a height of 5 meters before sliding, the following internal energy level results: $ E_ {inn} = {80kg} \ cdot {9.81} \ frac {m} {s ^ 2} \ cdot {5m} $. In this example, the energy that passes into the system as internal energy would be $ 3924 \ frac {kg \ cdot m ^ 2} {s ^ 2} = 3924J $.

With this calculation you can determine how much external energy is being supplied to a system. Note that not only potential energy can be converted into internal energy, but also kinetic energy, among other things.

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If a car is braked from $ 50 km / h $ to $ 0 km / h $ in front of a red traffic light, its kinetic energy is converted into internal energy of the vehicle by heating the brake discs.

But every system also has a fundamental internal energy potential. That is the total energy that is present in a system. This arises from the sum of the kinetic and potential energy of all particles in a body.

Now you know the most important things about internal energy, how it is created and how you can calculate it. You can now check your newly acquired knowledge on our tasks. We wish you a lot of fun and success!

Test your knowledge!

A body with a mass of 15 kg achieves an internal energy potential of $ 735.75 J $ when sliding. What was the initial height of the body?

A body slides down from a height of 11 meters and has an internal energy potential of $ 3561.03J $. What is the mass of this body?

How big is the internal energy when an object weighing 200 kg slides down from a height of 7 meters?

A climber stands on a ledge and slides down a rope to another ledge. In which order are the individual forms of energy converted into one another? Mark the correct answer.

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