1. The problem is to understand and apply the famous equation from physics: $E=mc^2$. 2. This equation states that energy ($E$) is equal to mass ($m$) multiplied by the speed of light squared ($c^2$). 3. Here, $c$ is the speed of light in vacuum, approximately $3 \times 10^8$ meters per second. 4. The formula shows the equivalence of mass and energy, meaning a small amount of mass can be converted into a large amount of energy. 5. For example, if $m=2$ kilograms, then energy is calculated as: $$E = 2 \times (3 \times 10^8)^2 = 2 \times 9 \times 10^{16} = 1.8 \times 10^{17}$$ 6. This means $2$ kilograms of mass corresponds to $1.8 \times 10^{17}$ joules of energy. 7. This principle is fundamental in nuclear physics and explains the energy released in nuclear reactions.