Physics Ch 2. Work and Energy Flashcards
Energy
The property of a system that enables it to do something or make something happen, including the capacity to do work, SI unit for all forms are joules
Kinetic energy
Energy associated with the movement of objects, depends on mass and speed squared, not velocity
Potential energy
Energy stored within a system, exists in gravitational, elastic, electrical, and chemical forms
Gravitational potential energy
Related to the mass of an object and its height above a zero-point called a datum
Datum
Zero point
Elastic potential energy
Related to the spring constant and the degree of stretch or compression of a spring sqaured
Spring constant
A measure of the stiffness of a spring
Electrical potential energy
Exists between charged particles
Chemical potential energy
Energy stored in the bonds of compounds
Total Mechanical Energy
The sum of its kinetic and potential energies
Conservative forces
Path independent and do not dissipate the mechanical energy of a system, total mechanical energy conserved if only conservative forces, examples include gradine and electrostatic forces, elastic forces are nearly conservative
Nonconservative forces
Path dependent and cause dissipation of mechanical energy from a system, total energy is conserved by some mechanical energy is lost as thermal or chemical energy, examples include friction, air resistance, or viscous drag
Work
A process by which energy is transferred from one system to another, may be expressed as the for product of force and displacement or the produce of force and distance traveled with the cosine of the angle between the two
Pressure-volume curve
Work is the area under this curve
Power
Rate at which work is done or energy is transferred, unit is the Watt
Work-energy theorem
States that when net work is done on or by a system, the system’s kinetic energy will change by the same amount, in more general applications, the work done on or by a system can be transferred to other forms of energy as well
Mechanical advantage
Factor by which a simple machine multiples the input force to accomplish work, makes it easier to accomplish a given amount of work because the input force necessary to accomplish the work is reduced, the distance through which the reduced input force must be applied however is increased but eh same factor
Simple machines
Include the inclined plane, wedge, wheel and axle, lever, pulley, and screw, provide the benefit of mechanical energy
Load
The output force of a simple machine, acts over a given load distance to determine the work output of the simple machine
Load distance
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Effort
The input force of a simple force, acts over a given effort distance to determine the work input of the simple machine
Effort distance
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Efficiency
Ratio of the machines work output to work input when nonconservative forces are taken into account
Kinetic energy equation equation
K = 1/2mv^2
Gravitational potential energy equation
U =mgh
Elastic potential energy equation
U = 1/2kx^2
Total mechanical energy equation
E = U+K
Conservation of mechanical energy equation
DELTAE = DELTAU+DELTAK = 0
Work done by nonconservative forces equation
Wnonconservative = DELTAE = DELTAU+DELTAK
Definition of mechanical work equation
W = F°d = Fdcostheta
Definition of work isobaric gas piston system equation
W = P*DELTAV
Definition of power equation
P = W/t = DELTAE/t
Work energy theorem equation
Wnet=DETLAK = Kf-Ki
Mechanical advantage equation
Mechanical advantage = Fout/Fin
Efficiency equation
Efficiency = Wout/Win = load*load distance/effort/effort distance
