What is the E MC2 formula

E = mc² or E = mc2

With E = mc2 we deal with and in this article. You will learn what is meant by this equation and what the individual variables stand for. Corresponding examples and tasks are also presented. This article belongs to our field of physics or relativity theory.

In order to be able to understand the following contents, a few previous knowledge is not that bad (a lot can be understood without it, but it helps to already know some basic terms of physics). So if you have problems understanding it, take a look at the following articles first:


E = mc2 by Albert Einstein

First of all, an important note: If you look through various forums on the Internet, you will read E = mc2 regularly. This is wrong. E = mc is correct2. However, the wrong spelling is usually not due to the fact that the authors do not know that the 2 is an exponent, but rather to representation problems. So always with E = mc2 work and never E = mc2.

With this equation by Albert Einstein, a connection between energy, mass and the speed of light is established. In addition, one should be aware of the fact that mass and energy were independent quantities in classical physics. There are also equations with potential and kinetic energy that establish such a relationship. However, these were independent of each other. But let's look at the sizes first.

Albert Einstein's formula:

  • E = mc2
  • "E" is the energy of the body in Newton meters or Joules, i.e. Nm or J
  • "m" is the dynamic mass of the body in kilograms, ie kg
  • "c" is the speed of light in meters per second, ie m / s

The equation says: Energy is equal to mass times the speed of light squared. And one more point should be made clear: There is an equivalence of mass and energy (equivalence principle). This means that mass and energy can be converted into one another. Every change in mass means a change in energy and vice versa.


E = mc2 Examples

For a better understanding, let's look at examples.

Task 1:

A mass of 1 kg should be assumed for a first calculation. With this the energy "E" is to be calculated. The speed of light may be rounded to c = 300,000,000 m / s.

Solution: We put m = 1 kg and the speed of light c = 300,000,000 m / s in the equation E = mc2 a.

  • E = mc2
  • E = 1 kg 300,000,000 m / s 300,000,000 m / s
  • E = 90,000,000,000,000,000 kgm2/ s2
  • E = 9 x 1016 kgm2/ s2
  • E = 9 x 1016 Nm
  • E = 9 x 1016 J

As a mathematical solution, we get E = 90,000,000,000,000,000 kgm2/ s2. We shorten this notation by using a notation with a power. I have also given a representation with Newton meter (Nm) and Joule (J).

Exercise 2:

During nuclear fission or also during nuclear fusion, mass changes occur. So an example for the nuclear fusion of the sun is to be calculated: Here hydrogen and helium merge. In the case of a mass defect of 4.2 million tons, the energy released should be calculated.

Solution: We put the weight of 4.2 million tons in the equation, this corresponds to 4.2 · 109 kg. For the speed of light we take the rounded value of 300,000,000 m / s (and square this):

  • E = mc2
  • E = 4.2 x 109 kg 300,000,000 m / s 300,000,000 m / s
  • E = 3.78 x 1026 J


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