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Conceptual Physics Chapter 7: Energy
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Conceptual Physics 12th e. by Paul G. Hewitt Summary of Terms, Summary of Formulas, and Terms Within the Textbook
Terms in this set (16)
Work
The product of the force and the distance moved by the force:
W = Fd
(More generally, work is the component of force in the direction of motion times the distance moved.)
Power
The time rate of work:
(More generally, power is the rate at which energy is expended.) Power = work done/time interval
Energy
The property of a system that enables it to do work.
Mechanical energy
Energy due to the position of something or the movement of something.
Potential energy (PE)
The energy that something possesses because of its position.
Kinetic energy (KE)
Energy that something possesses because of its motion, quantified by the relationship:
Kinetic energy = ½ mv²
Work-energy theorem
The work done on an object equals the change in kinetic energy of the object.
Work = ∆KE
(Work can also transfer other forms of energy to a system.)
Law of Conservation of energy
Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes.
Machine
A device, such as a lever or pulley, that increases (or decreases) a force or simply changes the direction of a force.
Conservation of energy for machines
The work output of any machine cannot exceed the work input. In an ideal machine, where no energy is transformed into thermal energy,
work input =work output
;
(Fd) input = (Fd) output
.
Lever
Simple machine consisting of a rigid rod pivoted at a fixed point called the fulcrum.
Efficiency
The percentage of the work put into a machine that is converted into useful work output.
(More generally, useful energy output divided by total energy input.)
Joule
The unit of work, also known as a Newton-meter.
Gravitational Potential Energy
The potential energy due to elevated positions.
Fulcrum
The point on which a lever rotates.
Ideal Machine
A machine that operates at 100% efficiency. 100% of the work input appears as work ouput.
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