The laws of energy are crucial to understanding how objects move in our physical world. The law of conservation of energy states that energy is never created or destroyed, it just changes from one form to another. In order to be able to comprehend this law, it is helpful to know a few types of energy. I'll introduce two very common types of energy to you, and then show you how they work with an aerial silks move.

First, there is kinetic energy, which is simply the energy of motion. When a person moves in any way, they have kinetic energy, as kinetic energy is dependent on speed. (v= velocity)

Second, there is energy in the form of gravitational potential energy. This is also referred to as the energy of position. When a person is elevated to any height, they will have an amount of gravitational potential energy, as potential energy is dependent on position. (g= acceleration due to gravity)

The unit of energy used in the SI system is called the joule, and it is equal to kg m²/s².

So how are these two forms of energy related? Their relationship forms the law of conservation of mechanical energy. This means that when an object moves in an isolated system, the amount by which potential energy changes will directly equal the amount of change in kinetic energy.

Here I show the law of conservation of energy in action with a silks move called the jump rope drop. I start out above the ground and have only potential energy at my starting point (ignore the small amount of kinetic energy I have in the horizontal direction as I am slightly swaying). Then as I let the tension out of the silk, I fall for a short distance. During the time that I am moving downwards, in the vertical direction, my potential energy is transferring into kinetic energy. At the end of my drop, the slack in the silk is used up and I am brought to a stop. At the point just before I come to a stop, I would have only kinetic energy.

[video from N. Gyswyt]

To put the motion in the video above into terms of the equation given for conservation of mechanical energy:

Kinetic energy initial is equal to zero.
Potential energy initial is equal to my mass*acceleration due to gravity*height.
Kinetic energy final is equal to one half*my mass*my velocity squared.
Potential energy final is equal to zero.

If I wanted to solve for my velocity right at the end of my drop, it would be a very simple problem.

By understanding how energy is transferred in a system, you can solve for many different unknown variables. Just begin with the simple equation of conservation of mechanical energy and analyze your system at its initial and final stage.