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Work, Energy and Machines |
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Work - a transfer of energy |
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the product of a force applied to an object and
the parallel distance the object is moved |
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Units of work (also energy) |
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Newton.meters (1 N.m = 1 Joule) |
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Pounds .feet (ft .lbs) |
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Kinetic Energy - energy due to motion |
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Units of energy (also work) |
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kg.(m/s)2 ( kg.m/s2 .m |
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N.m = Joule) |
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slug .(ft/s)2 (slug.ft/s2.ft |
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lb.ft = ft.lb) |
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Potential Energy - energy due to position |
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Units of energy (also work) |
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kg.m/s2 .m ( kg.m/s2 .m |
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N.m = Joule) |
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slug .ft/s2.ft (slug.ft/s2.ft |
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lb.ft = ft.lb) |
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Pneumatics |
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Work done is equal to the energy transfer |
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KE is the moving air |
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PE is stored in the tank |
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Hydraulics |
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Work done is equal to the energy transfer |
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KE is the moving fluid |
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PE is stored in accumulators |
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Energy is not created or destroyed. It may
change forms or be transferred to another object. (In a nuclear reaction
mass becomes energy or energy becomes mass) |
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Total energy remains constant |
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Applications (ignore wind resistance) |
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Max. Height |
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Max. Speed |
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Power - the rate of doing work |
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Units of power |
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Joules / second = watts (1 J/s = 1 W) |
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ft.lb / second (550 ft.lb/s = 1 hp) |
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Machines - a device for multiplying force or
speed and/or changing the direction of force |
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Law of Simple Machines |
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Seven simple machines |
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levers, pulleys, wheel and axle, inclined plane,
wedge , screw and hydraulic press |
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Efficiency |
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Mechanical Advantage |
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actual |
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ideal |
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1st class |
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2nd class |
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3rd class |
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Gears |
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IMA = |
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SR = |
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Compound Machines |
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Multiply the IMA of each simple machine |
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Notes