Mass Energy Formula

Team Physics -
Created by: Team Physics -, Last Updated: May 8, 2024

Mass Energy Formula

What is Mass Energy Formula?

The Mass Energy Formula, represented as

E = m x cΒ²

is a fundamental equation in physics that was discovered by Albert Einstein in 1905. This formula expresses the idea that mass and energy are interchangeable; it states that the energy of a system is equal to the mass of the object multiplied by the square of the speed of light . Here,

  • E = Energy.
  • m = Mass.
  • c = Speed of light in a vacuum, which is approximately 299,792,458 meters per second.

The equation is a key principle of Einstein’s theory of special relativity, showing that even a small amount of mass can be converted into a large amount of energy.

This formula has transformed our understanding of energy and mass, revealing that they are not distinct elements but rather different forms of the same thing. It underscores many modern technologies and theoretical applications, from nuclear power generation to the basic principles of particle physics. The Mass Energy Formula is pivotal because it provides a method to calculate the enormous energy potential of a tiny amount of mass.

Derivation of Mass Energy Formula

The derivation of the Mass Energy Formula, 𝐸=π‘šπ‘Β², begins by considering the principles of special relativity, introduced by Albert Einstein. First, let’s understand the relationship between energy, mass, and the speed of light within the framework of physics.

Starting with the concept of energy and momentum: In special relativity, the total energy (E) of a particle is related to its momentum (p) and mass (m) through the equation:


Here, 𝑐 represents the speed of light in vacuum.

Considering a particle at rest: When a particle is at rest, its momentum p is zero.

Substituting 𝑝=0 into the equation simplifies it to:


Taking the square root of both sides, we obtain:


This reveals that the energy of a particle at rest is solely dependent on its mass and the square of the speed of light.

This derivation shows that mass itself is a form of energy. Einstein’s formula 𝐸=π‘šπ‘2E=mc2 indicates that mass can be converted into energy and vice versa, highlighting the interchangeable nature of mass and energy.

Applications of Mass Energy Formula

  1. Nuclear Power Generation: This formula helps explain how nuclear reactors produce energy. In reactors, the nuclei of atoms split (nuclear fission) or combine (nuclear fusion), converting a small amount of mass into a large amount of energy.
  2. Nuclear Weapons: The destructive power of nuclear weapons comes from the conversion of mass into energy, following Einstein’s equation. A tiny amount of mass can release a tremendous amount of energy.
  3. Medical Applications: In treatments like cancer radiotherapy, machines use the principles of 𝐸=π‘šπ‘Β² to generate high-energy particles that can target and destroy tumor cells.
  4. Astrophysics: The formula helps astrophysicists understand processes like stellar evolution and black hole formation, where massive energy outputs result from mass conversion.
  5. Cosmology: The Big Bang theory utilizes 𝐸=π‘šπ‘Β² to explain how the early universe’s energy transformed into matter.

Example Problems on Mass Energy Formula

Problem 1: Calculating Energy from Mass

Question: Calculate the energy produced when 1 gram of matter is completely converted into energy.


Mass, π‘š=1 gram = 0.001 kg (since 1 gram = 0.001 kg)

Speed of light, 𝑐=299,792,458 m/s

Using the formula 𝐸=π‘šπ‘Β² :

𝐸=0.001 Γ— (299,792,458)Β²

𝐸=0.001 Γ— 8.9875517873681764 Γ— 10¹⁢ Joules

𝐸 β‰ˆ 89.875 Terajoules

Therefore, 1 gram of matter converted into energy yields about 89.875 Terajoules.

Problem 2: Comparing Mass Loss in Nuclear Reaction

Question: If 0.002 kg of mass is lost in a nuclear reaction, how much energy is released?


Mass loss, Ξ”π‘š=0.002 kg

Using 𝐸=π‘šπ‘Β²:

𝐸= 0.002 Γ— (299,792,458)Β²

𝐸 = 0.002 Γ— 8.9875517873681764 Γ— 10¹⁢ Joules

𝐸 β‰ˆ 179.75 Terajoules

The energy released from losing 0.002 kg of mass in a nuclear reaction is approximately 179.75 Terajoules.

Problem 3: Energy Content in a Sugar Cube

Question: Estimate the energy content in a sugar cube weighing 3 grams if all its mass could be converted to energy. Solution:

Mass of the sugar cube, π‘š=3 grams = 0.003 kg

Using 𝐸=π‘šπ‘Β²:

𝐸= 0.003 Γ— (299,792,458)Β²

𝐸 = 0.003 Γ— 8.9875517873681764 Γ—10¹⁢ Joules

𝐸 β‰ˆ 269.63 Terajoules

The theoretical energy content of a 3-gram sugar cube, if completely converted into energy, would be about 269.63 Terajoules.


How Do You Convert Mass to Energy?

Convert mass to energy by applying the Mass Energy Formula, 𝐸=π‘šπ‘Β². Multiply the mass by the square of the speed of light to find energy.

What is the Einstein’s Mass Energy Relation?

The Einstein mass energy relation, 𝐸=π‘šπ‘Β², states that energy equals mass multiplied by the speed of light squared, linking mass and energy.

Do Photons Violate 𝐸=π‘šπ‘Β²?

Photons do not violate 𝐸=π‘šπ‘Β²; they are massless but carry energy and momentum, consistent with Einstein’s theory of relativity.

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