Work and Machines

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QuizPatti  on April 1, 2012

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Lists terms about Work, Power, Simple Machines, and Mechanisms

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Work and Machines

 basic equation for workW = FD
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Definitions

basic equation for work W = FD
work the product of the force applied to the object in the direction of motion and the distance the object moves
joule the SI unit or work, defined as a newton-meter
foot-pound the British unit of work, the ft-lb
erg the the cgs unit of work, defined as a dyne-meter
equation for motion away from the direction of applied force W = FD cos Ɵ
the sum of individual work equals total work
work accomplished the area under the curve formed by plotting force against distance
integration the method in calculus that allows determination of the area under any curve
negative work force applied opposite to motion
net work the sum of positive work and negative work
power the time rate of doing work
average power P(av) = W/t
watt the SI unit of power (W), defined as one joule per second
foot-pound per second the British, or FPS, unit of power, (ft-lb/s)
erg per second the cgs unit of power, erg/s
horse-power (hp) 550 ft-lb/s; how much weight a horse could lift through a distance of one foot in one second
six simple machines lever, inclined plane, wedge, screw, pulley, and wheel and axle
fulcrum a point on which a lever pivots freely
load an object resting on one end of a lever, if a force is exerted at the other end
input force F(i), the force applied to a lever
output force F(o), the force applied to a load
input distance the distance through which an input force acts
output distance the distance through which an output force acts
input lever arm the distance from the fulcrum to the point of application of the input force
output lever arm the distance from the fulcrum to the load
input work the work done on a lever
output work the work done on a load
law of levers F(i)L(i) = F(o)L(o); the input force times the length of the input lever arm equals the output force times the length of the output lever arm
mechanical advantage the ability of a machine to multiply force
actual mechanical advantage AMA, the ratio of the output force to the input force, F(o)/F(i)
ideal mechanical advantage IMA, what the mechanical advantage would be if there were no energy losses due to friction, flexing of the lever, or other causes, D(i)/D(o) or L(i)/L(o)
Class 1 Lever a lever for which the input and load are located on opposite sides of the fulcrum
Class 2 Lever a lever for which the input and load are located on the same side of a fulcrum
Class 3 Lever a lever for which the input is located between the fulcrum and the load
IMA of an inclined plane IMA = S/H
input force for an inclined plane F(i) = F(w) sin Ɵ + u(k)F(w) cos Ɵ
AMA = 1/ sin Ɵ + u(k) cos Ɵ the actual mechanical advantage of an inclined plane
IMA of a wedge IMA = L/T
pitch of a screw the width of a single ridge and valley
IMA of a screw IMS = 2(3.14)r/P
block and tackle device consisting of a combination of several pulleys
wheel and axle a kind of rotary lever in which the input force is applied to the rim of one wheel and the output force is exerted at the rim of a larger or smaller wheel mounted on the same shaft
IMA = r(i)/r(o) IMA of a wheel and axle
torque a force that causes rotation of a wheel and axle, a screw, or any other object
efficiency of a machine work output divided by work input
efficiency equation efficiency = (Wo/Wi)(100%) or efficiency = (AMA/IMA)(100%)
mechanisms elements that serve to transmit motion
three basic types of mechanisms wrapping connector, direct-contact bodies, linkage
gear a rotating wheel or cylinder with projections encircling the rim
gear pair a combination of two gears
rack and pinion a gear moving on a track
driver the gear initiating motion
follower the gear other than the driver
gear train a series of gear pairs
spur gears gears that transmit motion between parallel shafts
helical gears gears in which the teeth follow a path that would be traced by a helix wrapped around the gear ring; they may be used to connect shafts at any angle
worm gear/endless screw gears in which force is exerted by the simultaneous action of several threads
bevel gears gears for transmitting motion around corners
pinion the smaller of a pair of gears when the gears are different sizes
gear the larger of a pair of gears when the gears are different sizes
gear ratio the number of teeth on the gear divided by the number of teeth on the pinion; the speed of the pinion relative to the speed of the gear
rotary speed revolutions per minute
rim speed measured in cm/s or cm/min, it is the same for both gears
positive drive the force applied by the driving tooth is normal to the surface of the following tooth, and the reactive force is normal to the surface of the driving tooth
uniform velocity ration the driver applies an unvarying force to the follower so that it rotates smoothly
involute the curve described by a point on a string as the string is unwound from a cylinder
cam/eccentric a simple mechanism for changing rotary motion into oscillations
slider-crank mechanisms a linkage mechanism consisting of a rotating crank, a reciprocating slider, and a shaft
stroke the movement of the slider from one extreme to the other
throw the distance across the circle of a crank along any diameter

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