1. Simple Machines W O R K M e c h a n i c a l A d v a n t a g e Force Effort E f f i c i e n c y 1

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

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 3

4. 6 types of simple machines 4

5. What is a machine? You still do the same amount of work —it’s just easier! 5

6. 1.Multiply the force you apply.  A Car Jack 2.Change the distance over which the force is exerted.  Hockey Stick 3.Change the direction of the force.  Blinds A machine can make work easier in three ways: 6

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

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

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

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

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. 11

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

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

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

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

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 16

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

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

19. REVIEW Position of Fulcrum 19

20. 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? Pulleys 1.Multiply the effort force 2.Change the direction of the force 20

21. Pulleys 21

22. Pulleys Two types of Pulleys: 1.Fixed pulley –A pulley that is attached to something –Does not change the amount of force applied –Changes the direction of the force 2.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*** 22

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

24. Mechanical Advantage of Moveable Pulleys MA =2 24 Movable pulley decreases the amount of force needed. 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. Output Force Input Force

25. Mechanical Advantage of Pulleys MA =4 25

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

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

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

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

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

31. 31

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

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34. A 25 B 10 C 5 D 4 A lever is used to lift a box. The mechanical advantage of the lever is 50 cm 5 cm. OR Mechanical Advantage means it took only 200 N of force to lift a 1000N object, therefore the machine multiplied the force 5 times! 34 Ideal Mechanical Advantage Length of effort arm Length of resistance arm

35. What is the amount of useful work output of a 25% efficient bicycle if the amount of work input is 88 N- m? A 2200 N-m B 113 N-m C 63 N-m D 22 N-m 35.25 = Output 88 J

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