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The tables we have seen previously are good to keep in mind. Energy and power are not quantities we deal with as much as mass and length and so it is important to get a good grasp of some example numbers.

Lets keep thinking about the asteroid energy as we move on to talk about different kinds of energy. Below is a list of different types of energy we will encounter:

1. Kinetic energy : Energy associated with movement. (e.g. bullet or asteroid).
2. Chemical energy : Energy stored in chemical bonds between atoms and molecules inside of matter (e.g. TNT, can of soda). Fundamentally this energy can be called electrical potential energy since the electric force is the force involved, as we will see.
3. Nuclear energy : Energy stored inside the nucleus of an atom. (e.g Uranium).
4. Gravitational potential energy : Energy stored in objects that wants to move under gravity. (e.g. water restrained by a dam).
5. Thermal energy (sometimes called heat).

Sophie: Hey, this is a really long list!

M: Well, just remember that energy is the ability to do work, that is the ability to start or stop something from moving . Water on top of a dam has energy because, if I open the dam, it will move down, potentially doing useful work like turning a turbine. Where does that energy come from? Well the mover is the force of gravity that pulls the water down so we call this type of energy gravitational potential energy. Water has the potential to move and do work because of gravity, because it is high above ground in this case.

M: We can divide this list into 2 types of energy, although this is ultimately just our organization as there are no fundamental differences between all these types of energies:

Energy of Movement . Obviously, this is kinetic energy but less obvious (and it was discovered much later), thermal energy (heat) is really also just energy of movement as we will see. You should even think of the mass energy E=mc^2 as energy related to movement.

Potential Energy . This is stored energy that can be converted into kinetic energy. Each force of nature can cause particles to move and as such there is a potential energy associated with each force. In fact, some might say that force is really a derived concept. All there is in the Universe is energy that wants to make things move. The water behind a dam has gravitational potential energy that is converted to kinetic energy when we open the dam. Chemical bonds between atoms in TNT have electrical potential energy that is released with the appropriate stimuli into kinetic energy (the explosion). And finally, nuclear energy is due to the release of energy from the nuclear force that binds protons and neutrons together.

But let us return to kinetic energy. This is the energy of movement, which will bring us to thermal energy. Again, the formula here is easy to remember, the energy of movement is proportional to the mass and goes like the velocity squared.

K=\frac12 mv^2

Very large objects or objects with very large speed can have tremendous amount of kinetic energy. More importantly, doubling the speed means that you quadruple the energy. This means that when you drive twice as fast, you will suffer much more than twice the damage in a collision!

Atoms move all the time and each atom has a certain amount of kinetic energy --> how much kinetic energy the atoms have relates to the different states of matter!