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Simple Machines Guilford County Sci Vis V205.07

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Simple Machines <ul><li>Devices such as levers, ramps, and pulleys that make our work easier. </li></ul><ul><li>They allow us to apply effort at one place to do work at another point and/or to change the direction of a force. </li></ul>

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<ul><li>One way is to magnify an effort force so that a smaller effort can be applied over a longer distance thus moving a large load a small distance. </li></ul><ul><li>Examples: </li></ul><ul><ul><li>a crowbar being used to dislodge a boulder, </li></ul></ul><ul><ul><li>a nutcracker being used to crack a nut, </li></ul></ul><ul><ul><li>or a block tackle pulley system being used to lift a large weight. </li></ul></ul>Simple Machines Source:http://www.lakelandschools.org/EDTECH/Machines/RubeMain.jpg

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<ul><li>The mechanical advantage of a machine is the ratio of the load force to the effort force. </li></ul><ul><li>The crowbar, nutcracker, and block and tackle pulley system have a mechanical advantage greater than one. </li></ul><ul><li>Other machines have a mechanical advantage less than one allowing magnification of the distance and speed of a movement. </li></ul><ul><li>An example of this might be a fishing rod or baseball bat. </li></ul>Simple Machines

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<ul><li>Inclined plane -- a sloping surface, such as a ramp. </li></ul><ul><ul><li>An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. </li></ul></ul><ul><ul><li>The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. </li></ul></ul><ul><ul><li>Examples: staircase, ramp, and bottom of a bath tub </li></ul></ul>Simple Machines Source: http://www.sirinet.net/~jgjohnso/inclineplanecolored.jpg

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<ul><li>Wedge -- two inclined planes joined back to back. </li></ul><ul><ul><li>Wedges are used to split things. </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Axe </li></ul></ul></ul><ul><ul><ul><li>Zipper </li></ul></ul></ul><ul><ul><ul><li>Knife </li></ul></ul></ul>Simple Machines

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<ul><li>Screw -- an inclined plane wrapped around a shaft or cylinder. </li></ul><ul><ul><li>This inclined plane allows the screw to move itself or to move an object or material surrounding it when rotated. </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Bolt </li></ul></ul></ul><ul><ul><ul><li>Spiral staircase </li></ul></ul></ul><ul><ul><ul><li>wood screw </li></ul></ul></ul><ul><ul><ul><li>Corkscrew </li></ul></ul></ul><ul><ul><ul><li>screws on light bulbs </li></ul></ul></ul>Simple Machines

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<ul><li>Wheel and axle -- a wheel and axle has a larger wheel (or wheels) connected by a smaller cylinder (axle) and is fastened to the wheel so that they turn together. </li></ul><ul><ul><li>When the axle is turned, the wheel moves a greater distance than the axle, but less force is needed to move it. </li></ul></ul><ul><ul><li>The axle moves a shorter distance, but it takes greater force to move it. </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Door knob </li></ul></ul></ul><ul><ul><ul><li>Wagon </li></ul></ul></ul><ul><ul><ul><li>Toy car </li></ul></ul></ul><ul><ul><ul><li>Bicycle gears </li></ul></ul></ul><ul><ul><ul><li>Screw driver </li></ul></ul></ul>Simple Machines

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<ul><li>Pulley -- a wheel that usually has a groove around the outside edge. </li></ul><ul><ul><li>This groove is for a rope or belt to move around the pulley. </li></ul></ul><ul><ul><li>Pulling down on the rope can lift an object attached to the rope. </li></ul></ul><ul><ul><li>Work is made easier since pulling down is assisted by gravity. </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Flag pole </li></ul></ul></ul><ul><ul><ul><li>Crane </li></ul></ul></ul><ul><ul><ul><li>Elevators </li></ul></ul></ul><ul><ul><ul><li>Window blinds </li></ul></ul></ul>Simple Machines Source: http://www.edinformatics.com/math_science/simple_machines/pulley.htm

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<ul><li>Lever -- a straight rod or board that pivots on a point known as a fulcrum. </li></ul><ul><ul><li>The fulcrum can be moved depending on the weight of the object to be lifted or the force you wish to exert. </li></ul></ul><ul><ul><li>Pushing down on one end of a lever results in the upward motion of the opposite end of the fulcrum. </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>Door on hinges </li></ul></ul></ul><ul><ul><ul><li>Seesaw </li></ul></ul></ul><ul><ul><ul><li>Hammer </li></ul></ul></ul><ul><ul><ul><li>Bottle opener </li></ul></ul></ul>Simple Machines

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Classes of Levers <ul><li>The class of a lever is based on the relative position of the load, effort, and fulcrum. </li></ul><ul><li>Levers are classified into 1st class, 2nd class and 3rd class levers. </li></ul>

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Classes of Levers <ul><li>1st class: </li></ul><ul><ul><li>Crowbar </li></ul></ul><ul><ul><li>Scissors </li></ul></ul>

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Classes of Levers <ul><li>2nd class: </li></ul><ul><ul><li>Nutcracker </li></ul></ul><ul><ul><li>Wheelbarrow </li></ul></ul><ul><ul><li>Doors </li></ul></ul>

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Classes of Levers <ul><li>3rd class: </li></ul><ul><ul><li>Tennis racket </li></ul></ul><ul><ul><li>Tweezers </li></ul></ul>

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Questions about Simple Machines <ul><li>What is a simple machine ? </li></ul><ul><li>What are the 6 simple machines ? </li></ul><ul><li>How does each simple machine work? </li></ul><ul><li>How does each machine make work easier? </li></ul><ul><li>What are the classes of levers and how do they work? </li></ul><ul><li>What is mechanical advantage? </li></ul>