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Simple Machines

Simple Machines. 1. Effort. Efficiency. Mechanical Advantage. WORK. Force. 2. Goals. Analyze the simple machines qualit atively and quant itatively in terms of force , distance, work and mechanical advantage. Be able to calculate mechanical advantage.

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Simple Machines

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  1. Simple Machines 1 Effort Efficiency Mechanical Advantage WORK Force

  2. 2 Goals • Analyze the simple machines qualitatively and quantitatively in terms of force, distance, work and mechanical advantage • Be able to calculate mechanical advantage • Explain the 6 different types of simple machines. • Be able to calculate amount of work done by a simple machine

  3. 3 Work • Transfer of Energy from one place to another. • Applying a force over a certain distance. • Calculating Work: • Work= Force x distance • W = f x d

  4. 4 6types of simple machines

  5. 5 What is a machine? A device that makes work easier. What is a simple machine? A simple machine does work with only one movement. You still do the same amount of work —it’s just easier!

  6. 6 A machine can make work easier in three ways: • Multiply the force you apply. • A Car Jack • Change the distance over which the force is exerted. • Hockey Stick • Change the direction of the force. • Blinds

  7. 7 Watch for this in all Simple machines: Machines are a “give and take relationship.” If you get your forcemultiplied, then you must go a greaterdistance.

  8. 8 Efficiency of a Machine A measure (%) of how much work put into a machine is actually changed to useful work put out by the machine. 90 J . 100 J NEVER OVER 100%

  9. 9 Ideal machine Efficiency =100% IMA= 100% According To “The Law of Conservation of Energy,” can this exist? Does not exist because of FRICTION.

  10. Mechanical Advantage 10 Number of times the machine multiplies the effort force is called the mechanical advantage. (Effort Force = is the force you apply to it) Ideal Mechanical = Effort Distance Advantage Resistance Distance OR Mechanical = Resistance Force Advantage Effort Force

  11. 11 Ideal and Actual Mechanical Advantage • Ideal Mechanical Advantage (IMA) occurs when there is no friction present. • IMA does not exist in the real world. There is always some friction present when operating a machine. • Length is the unit of measure. Ex: centimeters, meters • Actual Mechanical Advantage (AMA or MA) includes friction. • AMA or MA is the real world advantage • Force is the unit of measure. Measured in newtons.

  12. 12 Types of MachinesLevers A lever is a bar that is free to pivot, or turn about a fixed point. How can we use levers?

  13. 13 Levers Fulcrum Resistance Distance Effort Distance LOAD Effort Arm Resistance Arm Resistance Force Effort Force

  14. 14 Levers There are three types of Levers Based on the position of the fulcrum

  15. 15 Levers 1st Class:Crowbars, pliers, scissors, seesaw The fulcrum is between the resistance force and the effort force. The closer the fulcrum to the resistance force, the more the lever multiplies the force.

  16. 16 Levers 2nd Class: The resistance force or load is between the effort force and the fulcrum. • Wheelbarrow • Nutcrackers • Crowbar (forcing two objects apart) • The handle of a pair of nail clippers

  17. 17 3rd Class: the effort force is between the resistance force and the fulcrum. Levers • Hoe • Your arm • Catapult • Fishing rod • Tongs (double lever) (where hinged at one end)

  18. Mechanical Advantage of Levers 18 Ideal Mechanical Advantage = Length of Effort Arm Length of Resistance Arm Actual Mechanical Advantage = Resistance Force Effort Force Resistance Force Effort Force 5/5=1 10/5=2 20/5=4 LOAD Effort arm Resistance arm As the length of the effort arm increases, the IMA of the lever increases. *Maximum mechanicaladvantage is at the farthest point from the fulcrum.

  19. 19 REVIEW Position of Fulcrum

  20. 20 Pulleys • What is a pulley? • A pulley is a grooved wheel with a rope or chain running along the groove. • What can a pulley be used for? • Multiply the effort force • Change the direction of the force

  21. 21 Pulleys

  22. 22 Pulleys Two types of Pulleys: • Fixed pulley • A pulley that is attached to something • Does not change the amount of force applied • Changes the direction of the force • Movable pulley • The pulley is not attached • increases the amount of force applied. • Does not change the direction of the force Combination of both types of pulleys is called a ***Block and Tackle***

  23. Mechanical Advantage of Fixed Pulleys 23 Resistance Force MA =1 • Fixed Pulley only changes the direction of the force, it does NOT reduce the force needed to lift the load. Ideal Mechanical Advantage = number of rope sections that support the load Effort Force

  24. Mechanical Advantage of Moveable Pulleys 24 The main advantage of a movable pulley is that you use less effort to pull the load. The main disadvantage of a movable pulley is that you have to pull or push the pulley up or down. MA =2 Output Force Input Force Movable pulley decreases the amount of force needed.

  25. Mechanical Advantage of Pulleys 25 MA =4

  26. 26 Inclined Plane A sloping surface that reduces the amount of force required to raise and object. Resistance Distance (h) Effort Distance (l) IMA = Effort Distance AMA/MA = Resistance Force Resistance Distance Effort Force

  27. Mechanical Advantage of Inclined Planes 27 ------ --------- ---------------

  28. 28 Wheel and Axle • Consisting of two wheels of different sizes that rotate together • The effort force is applied to the larger wheel

  29. 29 Ideal Mechanical Advantage = Radius of wheel     Of wheel and axel         Radius of axel Gears are wheels with teeth.

  30. 30 Screw • An inclined plane wrapped around a cylinder • The inclined plane lets the screw slide into the wood. Examples: Bolt, Spiral Staircase

  31. 31

  32. 32 Wedge • An inclined plane with one or two sloping sides. • Changes the direction of the effort force. Examples: Axe, Zipper, Knife Effort Force Resistance force

  33. 33

  34. A lever is used to lift a box. The mechanical advantage of the lever is 34 5 cm. Mechanical Advantage means it took only 200 N of force to lift a 1000N object, therefore the machine multiplied the force 5 times! Ideal Mechanical Advantage Length of effort arm Length of resistance arm OR 50 cm A25 B10 C5 D4

  35. 35 What is the amount of useful work output of a 25% efficient bicycle if the amount ofwork input is 88 N-m? A 2200 N-m B 113 N-m C 63 N-m D 22 N-m Output .25 = 88 J

  36. 36 Which of the following is an example of a compound machine? A bicycle B crowbar C doorknob D ramp

  37. Simple Machines

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