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Simple Machines

Simple Machines. Matt Aufman and Steve Case University of Mississippi NSF NMGK-8 February 2006. Simple Machines. Have few or no moving parts Make work easier Can be combined to create complex machines

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Simple Machines

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  1. Simple Machines Matt Aufman and Steve Case University of Mississippi NSF NMGK-8 February 2006

  2. Simple Machines • Have few or no moving parts • Make work easier • Can be combined to create complex machines • Six simple machines: Lever, Inclined Plane, Wheel and Axle, Screw, Wedge, Pulley NSF North Mississippi GK8

  3. Lever Has three parts to it: • Fulcrum 2) the load 3) the effort Trade off: must move lever large distance to move load small distance • There are 3 types of levers NSF North Mississippi GK8

  4. 1st Class Lever Draw this picture: • The fulcrum is located between the effort and the load • Direction of force always changes • Examples are scissors, pliers, and crowbars NSF North Mississippi GK8

  5. 2nd Class Lever Draw this picture: • The resistance is located between the fulcrum and the effort • Direction of force does not change • Examples include bottle openers and wheelbarrows NSF North Mississippi GK8

  6. 3rd Class Lever Draw this picture: • The effort is located between the fulcrum and the resistance • Direction of force does not change, but a gain in speed always happens • Examples include ice tongs, tweezers and shovels NSF North Mississippi GK8

  7. Mechanical Advantage • To do these tasks without a machine would be difficult. • We know that a machine multiplies whatever force put into it (so you can complete the task) : - Using a screwdriver to turn a screw - Twisting a nail with pliers - Carrying a box up a ramp instead of stairs • The amount that the machine multiplies that force is the mechanical advantage of the machine • Abbreviated MA NSF North Mississippi GK8

  8. Mechanical Advantage: Lever M A = Effort Arm (effort to fulcrum) Load Arm (fulcrum to load) • What is the MA for the example? • Distance from effort to fulcrum: 10 feet • Distance from load to fulcrum: 5 feet The answer is: MA = 10/5 = 2 NSF North Mississippi GK8

  9. Inclined Planes • A slope or ramp that goes from a lowerto higher level • Makes work easier by taking less force to lift something a certain distance • Trade off: the distance the load must be moved would be greater than simply lifting it straight up NSF North Mississippi GK8

  10. Mechanical Advantage: Inclined Plane • The mechanical advantage of an inclined plane is the length of the slope divided by the height of the plane, if effort is applied parallel to the slope • Let’s say S = 15 feet, H = 3 feet So for our plane MA = 15 feet/3 feet = 5 NSF North Mississippi GK8

  11. Wheel and Axle • A larger circular wheel affixed to a smaller rigid rod at its center • Used to translate force across horizontal distances (like a car) • Trade off: the wheel must be rotated through a greater distance than the axle NSF North Mississippi GK8

  12. Mechanical Advantage: Wheel and Axle So for our wheel and axle MA = 10”/2” = 5 NSF North Mississippi GK8

  13. Screw • An inclined plane wrapped around a rod or cylinder • Used to lift materials or bind things together NSF North Mississippi GK8

  14. Mechanical Advantage: Screw So for our screwdriver MA = 3.14”/0.1” = 31.4 Circumference = ∏ x 1” = 3.14” Pitch = 1/10” = 0.1” NSF North Mississippi GK8

  15. Wedge • An inclined plane on its side • Used to cut or force material apart • Often used to split lumber, hold cars in place, or hold materials together (nails) NSF North Mississippi GK8

  16. Mechanical Advantage: Wedge • So for our wedge, MA = 6”/2” = 3 • They are one of the least efficient simple machines NSF North Mississippi GK8

  17. Pulley • A rope or chain free to turn around a suspended wheel • By pulling downon the rope, a load can be lifted with less force • Trade off: no real trade off here; the secret is that the pulley lets you work with gravity so you add the force of your own weight to the rope NSF North Mississippi GK8

  18. Mechanical Advantage: Pulley • The Mechanical Advantage of a pulley is equal to the number of ropes supporting the pulley • So for the pulley system shown there are 3 ropes supporting the bottom pulley MA = 3 • This means that if you pull with a force of 20 pounds you will lift an object weighing 60 pounds NSF North Mississippi GK8

  19. The trick is WORK • Simple machines change the amount of force needed, but they do not change the amount of work done • What is work? • Work equals force times distance • W = F x d • By increasing the distance, you can decrease the force and still do the same amount of work • HW: Feb. 7 (Thursday): Extra Credit: • Find a simple machine at home and determine the mechanical advantage. NSF North Mississippi GK8

  20. Eduardo is helping his family move out of their old house. Help him decide which task would be easier, and then help him figure out what simple machine makes the job easier. NSF North Mississippi GK8

  21. Eduardo has to move some heavy boxes into the moving truck. A B He would use an Inclined Plane NSF North Mississippi GK8

  22. Eduardo has to move a heavy box a long distance. A B He would use a cart with wheels and axles. NSF North Mississippi GK8

  23. Eduardo needs to tear off a piece of packing tape. A B He would use a scissors or wedges. NSF North Mississippi GK8

  24. Eduardo needs to move a heavy box to his room on the fourth floor. A B He would use a pulley NSF North Mississippi GK8

  25. Eduardo needs to help his father move the refrigerator. A B He would use a lever NSF North Mississippi GK8

  26. Eduardo needs to help his father change a flat tire on the moving truck. A B He would use a jack that uses a screw. NSF North Mississippi GK8

  27. Sources COSI.org. 2006. Simple Machines. Accessed 3 February 2006. http://www.cosi.org/onlineExhibits/simpMach/sm1.html Jones, Larry. January 2006. Science by Jones: Levers. Accessed 2 February 2006. http://www.sciencebyjones.com/secondclasslevers.htm Mikids.com. 2006. Simple Machines. Accessed 2 February 2006. http://www.mikids.com/Smachines.htm Professor Beaker’s Learning Labs. August 2004. Simple Machines: inclined planes. Accessed 2 February 2006. http://www.professorbeaker.com/planefact.html Wikepedia. Accessed 3 February 2006. http://en.wikipedia.org/wiki/Mechanicaladvantage NSF North Mississippi GK8

  28. Image Sources <http://etc.usf.edu/clipart> <http://www.oz.net/~peragine/doorknob.jpg> <http://www.theteachersguide.com/clipart/scissors.gif> <http://www.weprintcolor.com/stockimages/construction/images/Black%20metal%20crowbar.jpg> <http://67.19.222.106/military/graphics/flagpole.jpg> <http://www.morris.umn.edu/UMMimages/public/images/campus_misc/flagpole.jpg> <http://www.phillips-screw.com/images/homeMain.jpg> <http://mws.mcallen.isd.tenet.edu/mchi/ipc/ch15htm/images15/Screw.jpg> <http://www.discountramps.com/handi-van_ramp.gif> http://staff.harrisonburg.k12.va.us/~mwampole/1-resources/simple-machines/flag-pole.jpg NSF North Mississippi GK8

  29. Images Sources (cont.) <http://www.physics.uwaterloo.ca/demo/bikewheelgyro.html> <http://www.piratescave.co.uk/about_us.htm> <http://staff.harrisonburg.k12.va.us/~mwampole/1-resources/simple-machines/handicap-ramp.html> <http://library.thinkquest.org/J002079F/wedge.htm> <http://www.idahoptv.org/dialogue4kids/season7/simplemachines/facts.html> <http://www.scienceclarified.com/Io-Ma/Machines-Simple.html> NSF North Mississippi GK8

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