1. ENERGY

In prehistoric times, muscular energy was the only source of energy that people had.Energy is the capacity of a body to perform transformations and do work.

1.1.Forms of energy

Kinetic.The energy of physical movement.

Mechanical.The sum of potential and kinetic energy.

Sound.The energy of sound waves,which are produced by vibrations and propagated 
through a physical medium.

Electrical.The product of an electrical current.

Nuclear.The energy in the nucleus of an atom.

Luminous.Associated with light.

Thermal or Calorific.Associated with the movement of particles in matter.

Chemical.Results from the formation or descomposition of substances.

Electromagnetic.Occurs when electrical currents create magnetic fields.

1.2.Units of measurement for energy.

In the International System energy is measured in joules(J).When energy takes the form of heat, we often express it as calories. 1 cal=4.18 J

1.3.Power

The power of a achine is the amount of work that it can do in a certain amount of time.The relationship is :P=W/t
Some form of energy is present in all physical phenomenaPotential Energy.Associated with the height of an object above the ground, or the storage of energy in a spring.
Power is a measurement of how quickly work is done.