work, energy, and power. work (w) the product of the force (f) applied to an object over a distance...
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Work, Energy, and Power
Work (W)The product of the force (F) applied to an object over a distance (d) in which the object travels as a result of the force
W F d Joule (j) is the base unit of work
1 1 1joule newton meter
J N m
(Force and distance must be parallel to each other)
A student lifts a 50 pound (lb) ball 4 feet (ft) in 5 seconds (s).
How many joules of work has the student completed?
W F d 222.5 1.22W N m
271W J
1 4.45lb NConvert English units to SI units
1 0.305ft m
Solve for Work
Work Example
50.0 4.45 222.5 223 lb N N 4.00 0.305 1.22ft m
Energy
Ability to do work (light, heat, mechanical, chemical, electrical)
NASA solar sail Fuel cellRoller coaster
Forms of EnergyPotential Energy (Stored energy or gravitational energy)
The capacity to do work by virtue of position or configuration
Forms of EnergyKinetic Energy (Energy of motion)
Energy which a body possesses because of its motion, which occurs anywhere from an atomic level to that of a whole organism
Energy Transformation
Chemical
Radiant
Electrical
Renewable Energy SourcesBiomassBiomass HydropoweHydropower GeothermalGeothermal
WindWind SolarSolar
Nonrenewable Energy Sources
PetroleumPetroleum
Natural GasNatural GasCoalCoal
UraniumUranium
Conservation of EnergyEnergy cannot be created or destroyed, but it can change from one form to another.
Energy Efficiency: The ratio of the useful energy delivered by a dynamic system to the energy supplied to it
Entropy: The loss of energy during conversion
outputEfficiency% x100
input
Energy ConversionChanging one form of energy to another
Energy ConversionExamples
Fossil fuels Chemical → Heat → Mechanical → Electrical
Solar cells Sunlight → Electrical
Wind turbines Kinetic → Mechanical → Electrical
Hydroelectric Gravitational potential → Mechanical → Electrical
Nuclear Nuclear → Heat → Mechanical → Electrical
Vehicle System Conversion
Chemical
Mechanical HeatWhich output is desired, mechanical or heat?
What Are Current Energy Concerns?
ConsumptionConsumption
What roles do engineers have in energy?What roles do engineers have in energy?
PollutionPollutionDepletionDepletionDependencyDependencyCostCost
http://www.eia.doe.gov
PowerRate at which work is performed or energy is expended
WP=
tWatt is the base unit of Power
One watt is equal to 1 joule of work per second
Types of Power
Electrical Power
Uses electrical energy to do work
Mechanical Power
Uses mechanical energy to do work (linear, rotary)
Fluid Power
Uses energy transferred by liquids (hydraulic) and gases (pneumatic)
Power Example
Power = Work / Time
Work = 271.45J
P
P
271.45 J5.00s
J54.3
s
P
J1 1Watt( W)s
54.3W
A student lifts a 50.0 pound (lb) ball 4.00 feet (ft) in 5 .00seconds (s). How many watts of power are used to lift the ball?
Resources
McGraw-Hill dictionary of engineering. (2nd ed.). New York, NY: McGraw-Hill.
Microsoft, Inc. (2008). Clip art. Retrieved January 10, 2008, from http://office.microsoft.com/en-us/clipart/default.aspx
National Aeronautics and Space Administration (NASA). (1997). Daedalus. Retrieved April 2, 2008, from http://www.dfrc.nasa.gov/Gallery /Photo/Daedalus/
U.S. Department of Energy. (2008). Scientific forms of energy. Retrieved March 23, 2008, from http://www.eia.doe.gov/kids/energyfacts/science/formsofenergy.html
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