Energy, measured in Joules., comes in many different forms, but the su total of all energy is constant. Energy may be converted from form to form, but no energy is ever lost, though some energy may be lost to friction and be difficult to be turn it into a useful form. Common forms of energy are:
| Energy Type | Description | Example | Equation |
| Kinetic | Due to a Body of mass m moving with velocity v | A car moving | \[\frac{1}{2}mv^2\] |
| Gravitational | Due to the height h a body of mass has above the ground | A plane glying at 30,000 feet | \[mgh\] |
| Elastic | Due to elastic bodies being deformed | A spring with force constant k stretched a distance x | \[\frac{1}{2}kx^2\] |
| Chemical | Due to potential for chemical reaction | combustion | |
| Nuclear | Radioactive decay and nuclear reactions - fission and fusion | Atom Bomb | \[E=mc^2\] |
| Heat/Internal | Due to the temperature of a body or substance | Hot cup of tea | \[mcT\] where \[m, \: c, \: T\] are mass, specific heat capacity and temperature respectively |
| Electrical | Current flowing or charge being stored | capacitor storing charge | \[IVt\] where \[I, \: V, \: t\] are current, voltage and time respectively, or \[QV\] where \[Q, \: V\] are charge and voltage respectively |
| Light | Whenever it is light, there is light energy | The Sun shines | \[IAT\] where \[I, \: A, \: t\] are light intensity, area and time respectively |
| Sound | Mechanical vibration of gas or liquid molecules | When we speak |