WHAT IS ENERGY? Energy is the ability to do work. Forces ( Strong, Weak, Electromagnetic & Gravitational) move energy around in the universe. Thermal energy and elastic spring energy (Hooke's Law: F=-kx) are types of electromagnetic interactions.

WHAT IS WORK? Physics defines work as the "dot product" of force and displacement (both of which are vectors). Dot Products create non-vector commodities. As such, work and energy are not vectors. Work = F "dot" d = F d cos theta (where theta is the angle between force and displacement).

CONSERVATION OF ENERGY --
Energy in a closed system remains constant. 'A CLOSED SYSTEM" IS ONE WHERE ENERGY IS NOT ADDED OR REMOVED. The easiest way to cope with this conservation concept is to create an "energy audit".
Energy at position one = energy at position two.
In looking at Newtonian physics, our choices for types of energy are
------Kinetic Energy = 1/2 mass x velocity squared
 ------Gravitational Potential Energy = mass x g x height (g= + 9.8 m/s^2)
 ------Spring Potential Energy = 1/2 x spring constant 'k' x stretch (or compression) squared
 ------Energy Lost to Friction or Thermal Energy = the absolute value of friction x distance that
friction works to slow the object

So our audit looks at the values for each of these types of energies, finds the total at position one, finds the total at position two--- and then creates an equation where the total energy at position one = the total energy at position two !

NON-CONSTANT FORCES
If the force doing the work is not constant then the work done =     F dx. This means that for a Hooke's Law spring (F = - kx) the integral is necessary to find the work done in stretching the spring. So Work = kx 2 / 2

POWER
 Power is the Rate of Doing Work . As such, the following are true
P = work / time
P= F x d/t so P = F x v

Problem Practice : Set 1     Set 2      Set 3   

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