U4AOS1 Topic 5: Mass Energy

The most famous equation in the world discusses the relationship between mass, light and energy. But what does it actually mean??

It's basically building off of the kinetic energy equation we looked at earlier and looking at different perspectives. All it means is that energy is stored in the form of mass and this is the amount of potential (when at rest) and kinetic (when moving) energy it has.

$KE = \frac{1}{2}mv^2$

An example of this is the Sun. It is constantly losing mass as it provides sunlight. It doesn't gain energy from any source, so the only thing it could be using energy from is the mass.

APPLICATION

There are 3 scenarios that must be considered.

1. Rest Energy

As we said above, all objects at rest have potential energy. This is calculated with a simple equation.

$E = mc^2$

2. Total Mass Energy

Since Newtonian Physics breaks at high speeds, we must consider the Lorentz Factor.

$E = \gamma mc^2$

3. Kinetic Energy

Using the 2 equations above we can subtract our rest energy from our total energy to find the kinetic energy.

$E = (\gamma-1) mc^2$$E = \gamma mc^2 - mc^2 = (\gamma-1) mc^2$