Mass - Energy

Einstein showed from his theory of special relativity that it is necessary to treat mass as another form of energy. Before the advent of this theory of special relativity, it was presumed that mass and energy were conserved separately in a reaction. However, Einstein showed that mass is another form of energy and one can convert mass-energy into other forms of energy, such as kinetic energy, and vice versa.

Einstein gave the famous mass-energy equivalence relation:

Where: 

• E = energy equivalent of mass mm 
• m = mass 
• c = velocity of light in vacuum 
• c ≈ 3 × 10⁸ m s⁻¹

Experimental verification of Einstein’s mass-energy relation has been achieved in the study of nuclear reactions amongst nucleons, nuclei, electrons, and other more recently discovered particles.

In a reaction, the conservation law of energy states that the initial energy and the final energy are equal, provided the energy associated with mass is also included.

This concept is important in understanding nuclear masses and the interaction of nuclei with one another.

Calculate the energy equivalent of 1 g of substance. 

Solution

Given: Mass = 1 g = 10⁻³ kg

Using: E = mc²

Substituting the values:

E = 10⁻³ × (3 × 10⁸)² J
E = 10⁻³ × 9 × 10¹⁶ J
E = 9 × 10¹³ J

Result

If one gram of matter is converted into energy, an enormous amount of energy is released.