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# Levers

Simple Machines . Levers. Objectives. …distinguish between the different parts of a. lever. …describe the difference between a 1 st , 2 nd , . and 3 rd Class Lever. …explain the difference between Mechanical. Advantage and Disadvantage. …calculate the Ideal and Actual Mechanical.

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## Levers

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1. Simple Machines Levers

2. Objectives …distinguish between the different parts of a lever. …describe the difference between a 1st, 2nd, and 3rd Class Lever. …explain the difference between Mechanical Advantage and Disadvantage. …calculate the Ideal and Actual Mechanical Advantage, Velocity Ratio and Efficiency of a lever. You will be able to… …explain what a lever is.

3. What is a Lever? All levers are made up of 4 components: LOAD FULCRUM EFFORT LEVER ARM

4. EFFORT LOAD FULCRUM LEVER ARM Parts of a Lever If the FULCRUMis located at the midpoint of the LEVER ARM, and the EFFORT is equal to the LOAD, then the lever will be perfectly balanced. The LEVER ARM is a rigid bar that rests on and rotates about the FULCRUM. It serves to transfer the force of the EFFORT to the LOAD. The LOAD is the weight of the object(s) that is being moved (displaced). It represents a force that is measured in pounds (lbs) TheFULCRUM is the pivot point or moment around which the forces rotate. TheEFFORTis an outside force (person, machine, natural phenonoma) applied to the lever. It is also measured in pounds (lbs).

5. can be used to change the direction of an applied force (EFFORT) … can increase or decrease an applied force … can increase or decrease the distance travelled by an object (LOAD) Advantages of Levers:

6. 150 lbs When we lift heavy objects, we must produce an upward force that is equal to or greater than the weight of that object. For example... Imagine you are trying to lift a box that weighs 150 lbs. Your muscles must produce an upward force of 150 lbs or more in order to raise the box to the desired height. 150 lbs

7. Your muscles must produce an upward force of 150 lbs or more in order to raise the box to the desired height. If your muscles cannot produce the necessary upward force to overcome the weight of the box, then problems can occur. Levers can help!

8. Classes of Levers

9. 1st Class Levers

10. In a 1st Class Lever, the FULCRUM is located between the LOAD and the EFFORT. LOAD EFFORT FULCRUM

11. In a 1st Class Lever, the FULCRUM is located between the LOAD and the EFFORT. Note that the forces of the LOAD and the EFFORTare moving in the same direction. EFFORT LOAD FULCRUM

13. EFFORT LOAD When the FULCRUM is moved to one side, mechanical advantage or disadvantage occurs. Note: smaller EFFORT, butgreater distance that it must move EFFORT LOAD FULCRUM

14. Other examples of 1st Class Levers... Paint Can Opener

15. 2nd Class Levers

16. In a 2nd Class Lever, the LOAD is located between theFULCRUM and the EFFORT. LOAD FULCRUM EFFORT

17. Note that the forces from the LOAD and the EFFORT are pointing in opposite directions. LOAD FULCRUM EFFORT

18. FULCRUM LOAD EFFORT Bottle Opener

19. Other examples of 2nd Class Levers... Wheelbarrow

20. Other examples of 2nd Class Levers... Nut Cracker

21. A 2nd Class Lever always has mechanical advantage. LOAD FULCRUM EFFORT

22. 3rd Class Levers

23. In a 3rd Class Lever, the EFFORT is located between theFULCRUM and the LOAD. LOAD FULCRUM EFFORT

24. As was the case with the 2nd Class Lever, the forces from the LOAD and the EFFORT are pointing in opposite directions. LOAD FULCRUM EFFORT

25. Unlike the class 2 lever, a 3rd Class Lever has mechanical disadvantage. The EFFORT must be greater than the force of the LOAD. LOAD FULCRUM EFFORT

26. However, the distance moved by the LOAD is greater than the distance moved by the EFFORT. LOAD FULCRUM EFFORT

27. EFFORT LOAD FULCRUM Human Arm

28. Levers Combination in

29. EFFORT FULCRUM LOAD Lever #1 =2nd Class Lever Nail Clippers

30. EFFORT FULCRUM LOAD Lever #1 =2nd Class Lever Nail Clippers Lever #2 =3rd Class Lever

31. Levers & Mathematics

32. Moment: The tendency to produce motion around an axis or point. The turning effect produced by a lever is called a moment. It is the product of the applied force and the distance of that force from the fulcrum. Moment = force x distance = Work

33. 5 ft 20 lbs 1st Class Lever EFFORT force x distance = Moment = Work 20 lbs x 5 ft = 100 (EFFORT Moment) = 100 Joules

34. 2 ft 50 lbs 1st Class Lever LOAD force x distance = Moment = Work 50 lbs x 2 ft = 100 (LOAD Moment) = Joules

35. 1st Class Lever 5 ft 2 ft EFFORT LOAD 20 lbs EFFORT Moment =LOAD Moment 50 lbs Balanced Lever

36. …the ratio between the EFFORT-arm length to the LOAD-arm length. rE 5 ft IMA = rL 2 ft 5 IMA = 2 Ideal Mechanical Advantage: …IMA …also known as Theoretical Mechanical Advantage (TMA) 2.5 : 1

37. 6 in. 0.75 in. rE IMA = rL 6 IMA = .75 = 8 or ratio 8 : 1

38. rE IMA = rL 2 IMA = 20 2 in. 20 in. = 0.1 or ratio 0.1 : 1

39. …the ratio between the force applied to the LOAD arm and the force applied to the EFFORT arm FL AMA = FE EFFORT LOAD 20 lbs 50 AMA = 20 50 lbs Actual Mechanical Advantage: …AMA = 2.5 or ratio 2.5 : 1

40. …friction at the FULCRUM will cause the AMA to be less than the IMA, resulting in an efficiency less than 1 AMA = IMA Efficiency: …(Greek lowercase H…pronounced Eta) …the ratio of AMA to IMA Efficiency =

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