Work and simple_machines

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Work and simple_machines

  1. 1. PhysicsG9 MYP Sciences 2013 Mr. Erdosy 1 1
  2. 2. G9 Physics Unit Topics Newton’s Laws Momentum Electrostatics Simple Machines 2 3
  3. 3. Rube Goldberg Project Create a Goldberg-style Contraption with at least 3 stages to accomplish a simple task. 1 – Newton’s Laws 2 – Momentum 3 – Electrostatics Each must employ a Simple Machine. 3 4
  4. 4. Work and Simple Machines 4 9
  5. 5. ENERGY The textbook definition of Energy is: THE ABILITY TO DO WORK. 5 10
  6. 6. WORKWork is thetransfer of Energyby applying a Forceover a Distance 6 11
  7. 7. Formula for work Work = Force x DistanceThe unit of force is Newtons The unit of distance is meters The unit of work is Newton-meters One Newton-meter is equal to one Joule So, the unit of work is a Joule 7 12
  8. 8. W=Fd Work = Force x DistanceCalculate: If a manpushes a concrete block10 meters with a forceof 20 N, how muchwork has he done? 8 13
  9. 9. W=Fd Work = Force x DistanceCalculate: If a manpushes a concrete block10 meters with a forceof 20 N, how muchwork has he done? 200joules (W = 20N x 10m) 9 14
  10. 10. Fun Fact of the Day eat directly The amount of calories you determines the amount of work you are able to do.  1 calorie = 4.18 Joules 10 15
  11. 11. History of WorkBefore engines and motors were invented, people had to dothings like lifting or pushing heavy loads by hand. Using ananimal could help, but what they really needed were someclever ways to either make work easier or faster. 11 16
  12. 12. Simple Machines Ancient people invented simple machinesthat would help them overcome resistive forcesand allow them to do the desired work againstthose forces. 12 17
  13. 13. Simple Machines A simple machine makes Work easier by providing a Mechanical Advantage.  Changing the direction of a force.  Increasing the magnitude of a force while decreasing the distance it is applied.  Decreasing the input force by increasing the distance it is applied. 13 18
  14. 14. Simple Machines The six simple machines are:  Lever  Wheel and Axle  Pulley  Inclined Plane  Wedge  Screw 14 19
  15. 15. The 3 Classes of Levers The class of a lever is determined by the location of the effort force and the load relative to the fulcrum. 15 20
  16. 16. 3 ClassesTo find the MA of a lever, divide the output force by the input force, or dividethe length of the resistance arm by the length of the effort arm. 21
  17. 17. First Class Lever In a first-class lever the fulcrum is located at some point between the effort and resistance forces.  Common examples of first-class levers include crowbars, scissors, pliers, tin snips and seesaws.  A first-class lever always changes the direction of force (I.e. a downward effort force on the lever results in an upward movement of the resistance force). 17 22
  18. 18. Fulcrum is between EF (effort) and RF (load) Effort moves farther than Resistance. Multiplies EF and changes its direction 18 23
  19. 19. Second Class Lever With a second-class lever, the load is located between the fulcrum and the effort force. Common examples of second-class levers include nut crackers, wheel barrows, doors, and bottle openers. A second-class lever does not change the direction of force. When the fulcrum is located closer to the load than to the effort force, an increase in force (mechanical advantage) results. 19 25
  20. 20. RF (load) is between fulcrum and EF Effort moves farther than Resistance.Multiplies EF, but does not change its direction 20 26
  21. 21. Third Class Lever With a third-class lever, the effort force is applied between the fulcrum and the resistance force.  Examples of third-class levers include tweezers, hammers, and shovels.  A third-class lever does not change the direction of force; third-class levers always produce a gain in speed and distance and a corresponding decrease in force. 21 27
  22. 22. 3rd Class Lever has the effort in the middle effort arm is between the effort and the fulcrum resistance arm is between the effort and the resistance 22 30
  23. 23. EF is between fulcrum and RF (load) Does not multiply forceResistance moves farther than Effort. Multiplies the distance the effort force travels 23 28
  24. 24. Atlatl 24 29
  25. 25. Wheel and Axle The wheel and axle is a simple machine consisting of a large wheel rigidly secured to a smaller wheel or shaft, called an axle. When either the wheel or axle turns, the other part also turns. One full revolution of either part causes one full revolution of the other part. 25 31
  26. 26.  A pulley can be used to simply change the direction of a force or to gain a mechanical Fixed Pulley advantage, depending on how the pulley is arranged. A pulley is said to be a fixed pulley if it does not rise or fall with the load being moved. A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage. 26 32
  27. 27. Moveable Pulley A moveable pulley rises and falls with the load that is being moved. A single moveable pulley creates a mechanical advantage; however, it does not change the direction of a force. The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley. 27 33
  28. 28.  An inclined plane is an Inclined even sloping surface. The inclined plane makes it easier to Plane move a weight from a lower to higher Plane elevation. 28 34
  29. 29.  The mechanical advantage of an inclined plane is equal Inclined to the length of the slope divided by the height of the Plane inclined plane. While the inclined plane produces a mechanical advantage, it does so by increasing the distance through which the force must move. 29 35
  30. 30.  The wedge is a modification of the inclined plane. Wedges are used as either Wedge separating or holding devices. A wedge can either be composed of one or two inclined planes. A double wedge can be thought of as two inclined planes joined together with their sloping surfaces outward. 30 36
  31. 31. Screw The screw is also a modified version of the inclined plane. While this may be somewhat difficult to visualize, it may help to think of the threads of the screw as a type of circular ramp (or inclined plane). 31 37

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