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24 Cards in this Set
- Front
- Back
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Screw
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~Inclined plane wrapped around a post.
~reduces effort force (Fe) and direction. |
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Work Output/Input/Efficency
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Wo= Fe times Dr
Wi= Fe times De *input is always greater Efficiency= Wo/Wi times 100 *Never greater then 100% Low Friction= high efficiency |
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Inclined Plane
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~Changes the amount of effort force (Fe) and direction.
~2 types |
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First Class Lever
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~The fulcrum is between the effort force and the resistence force
Ex. crowbar, scissors, see-saw |
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Inclined Plane
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A smaller force is used but a larger distance is used.
IMA= length of plane/ height of plane Ex. steps, ramps |
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Wedge
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~2 inclined planes back to back
~reduces effort force (Fe) and direction |
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Second Class Lever
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~The resistance force is between the fulcrum and the effort force.
Ex. door, wheel, barrow, nutcracker |
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Third Class Lever
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The effort force is between the fulcrum and resistance force.
Ex. shovel, broom, bat, fishing pole |
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IMA of a lever
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~Can be determined by the effort arm length divided by the resistence arm length
~The MA can be less than one in some cases |
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Mechanical Advantage
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The number of times a machine multipliesthe effort force.
MA=Fr/Fe ( No units) Fr= resis. Fe= effort |
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IMA
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~Is the ideal (without friction) formula which varies with the machine
~Always greater than MA |
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Machine
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A machine is a device that helps you do work by changing the size or direction of the force.
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A lever is.....
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~a rigid bar free to pivot
~the fixed point of the pivot is the called the fulcrum. ~There are three classes of levers depending where the fulcrum is. |
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Lever
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~Changes the amount of effort force (Fe) and direction.
~ 3 classes of levers. |
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IMA of a wheel and axle...
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IMA=radius of wheel/ radius of axle
Ex.ferris wheel, water wheels and gears, wheel chair |
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Pulley
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~Wheel and axle working together
~reduces effort force (Fe) and direction. |
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Wheel and Axle
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~The lever that rotates in a circle
~made of 2 wheels of different sizes (axle is smaller) ~effort force applied to the wheel which moves a greater distance |
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Wheel and Axel
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~several levers working together
~reduces effort force (Fe) |
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Screw
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an inclined plane wrapped around a cylinder
IMA= the closer the ridges the greaterthe IMA Ex. jar lid, screw, drill bit |
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Wedge
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~2 inclined planes put together
~an effort force is applied to the thicker end and transferred to the thinner end. |
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Pulleys
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~chain, belt, or rope wrapped around a wheel
~changes direction OR amount of force |
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IMA if A wedge..
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The longer and thinner the wedge the greater the IMA
Ex. knife, zipper, wdge |
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Fixed/Movable Pulley
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Fixed Pulley- pulley attached to a stationary structure MA is one because it only changes direction
Movable Pulley- multiplies force |
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IMA of a pulley...
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IMA= # of supportive ropes
Ex. flag pole |
