AP Edition College Physics p. 290-297
The Basic Energy Model
1. The Basic Energy Model (Intro)
a. The fundamental forms of energy are kinetic, potential, and thermal energy. b. Most of the time will be spent understanding the transforming of energy. c. Energy can be transformed by applying a mechanical force. d. The law of conservation of energy, energy is neither created nor destroyed, is consider by scientists to be the most important law of nature. 2. Systems and Energy
a. Every system has a total energy which is the sum of all energies involved in the system. b. A system can have multiple types of energy that need to all be included in the total energy. 3. Energy Transformations
a. Energy of one kind can be transformed into another kind of energy to save everyone from having a dull life. b. It is easier to convert kinetic, potential, and chemical energy into thermal energy, but it is harder to change it from thermal back to one of the other three. 4. Energy Transfers and Work
a. An exchange of energy between system and environment is called an energy transfer. b. The two primary processes of energy transfer are work, which is the mechanical transfer of energy, or heat, which is the nonmechanical transfer of energy caused by differences in temperature between system and environment. c. The basic energy model shows how energy transfers in and out of a system and also energy transformations within the system. d. In physics, work is the process of transferring energy from system to energy or vice versa. e. Energy is transferred as work only when the system moves while the force acts otherwise there is no work being done. 5. The Law of Conservation of Energy
a. Work done on a system changes the system’s energy by exactly the amount of work that was done. b. An isolated system is a system that has no environment acting on it causing there to be no transfer of energy only transformations of energy. c. The total energy of an isolated system is conserved.
1. Work (Intro)
a. Only external forces can change the total energy of a system. b. The larger the displacement, the greater the work done. c. The stronger the force, the greater the work done.
d. The joule is the unit for all forms of energy.
e. Work is a scalar quantity.
2. Force at an Angle to the Displacement
a. A force does the greatest amount of work while acting in the same direction as the displacement. b. The sign (positive or negative) of W is determined entirely by the angle Theta between the force and the displacement. c. The total work is the sum of work done by each force. d. The total work is also the total energy transfer to the system from the environment or from the system to the environment. 3. Forces That Do Not Work
a. Force on an object doesn’t always do work.
b. If the object undergoes no displacement while the force acts, no work is done. c. A force perpendicular to the displacement does no work. d. If the part of the object on which the force acts undergoes no displacement, no work is done.