Credit: Vik Walker
License: CC BY-NC 3.0
Energy is a common concept in the modern world. A key to understanding energy in detail is how different kinds of energy transform from one to the other, such as circular motion being changed into electrical power.
- Work is defined as , the product of the component of the force along the line of motion and displacement.
- Work has units of N*m, or , also known as Joules (J).
- Energy comes in two forms: kinetic and potential
Kinetic energy is the energy of motion and potential energy is the energy of position. Potential energy can also have many forms. For example: gravitational potential energy, elastic potential energy, chemical potential energy, and nuclear potential energy to name a few.
- Energy is the ability to do work and has units of joules, J.
- Kinetic energy has the form:
- Gravitational potential energy has the form:
- The potential energy stored in a spring has the form:
- The relationship between the applied force and the distance a spring is stretched or compressed is: (Hooke’s Law)
- The Work-Energy principle is
- Dissipative forces such as friction are considered non-conservative forces. Mechanical energy is not conserved in the presence of non-conservative forces.
- The conservation of mechanical energy can be written as:
- In the presence of dissipative forces the conservation of energy can we written as:
, where is the energy that has been transformed into heat.
- In the event of an explosion, heat, , is added to the initial and energies and in the most general case, heat can also be lost, , after the explosive, thus:
- The average power is the rate at which work is done or consumed or produced : and has units of Watts