Work – The movement of an object by a force.

1. Work – The movement of an object by a force.

2. Work = Force x Distance

3. Joule = 0.74 ft*lb Used to describe work.

4. You decide to lift a 200 lbs dumbbell from the ground to over your head. The dumbbell will travel 7 feet. How much work did you do? 1400 ft*lb 1,036 joules

5. Power = Work / Time

6. Horsepower - Unit used to express power. Based on the estimation a horse could lift 550 pounds a distance of one foot in one second.

7. A weed eater uses 4400 ft*lb/sec of power, how many horsepower does it have? 8hp

8. Machines – Devices for doing work.

9. Simple Machines – Basic force multiplying machines.

10. Can help us by: • Multiplying the force applied to them. • Changing the direction of the force applied to them. • 3. Multiplying the speed or distance that the applied force moves something.

11. Effort (E) – The force we apply to the machine.

12. Resistance (R) – The force the machine helps us overcome.

13. Mechanical Advantage (MA) – Tells us the number of times a machine multiplies our effort. MA = Resistance / Effort

14. 3 men use a pulley system to lift a 1500 pound cargo container. The men use 125 pounds of effort, how much does the pulley system multiply the men’s effort? 12 Times

15. Work Input – The work put into a machine. Work Input = Effort Distance X Effort Force

16. Work Output – The work received from a machine. Work Output = Resistance Distance X Resistance Force

17. Law of Work – Work put into a machine is equal to the work received from the machine under ideal conditions. Effort Force x Effort Distance = Resistance Force x Resistance Distance Work Input = Work Output

18. Because of friction, no machine has ever been made that can produce exactly as much work as applied to it. Work Input is always greater than work output.

19. Although the work input is greater than the work output, no energy is lost, its just converted to other forms such as heat or sound. Work Input = Work Output + Work Used to Overcome Friction

20. 6 Types of Simple Machines • Lever • Wheel and Axle • Pulley • Inclined Plane • Wedge • Screw

21. Lever Can multiply the force or speed with or without changing the direction of the effort.

22. Fulcrum The pivot point upon which the beam of a lever rests.

23. First Class Levers Input and output forces are on either side of the fulcrum

24. Effort Arm The end of the lever that the effort force is applied to.

25. Resistance Arm The arm of the lever that moves by overcoming the resistance force.

26. If the effort arm is longer than the resistance arm the force will be multiplied. If the effort arm is shorter than the resistance arm the speed will be multiplied.

27. Second Class Levers Fulcrum is at one end of the lever, effort is applied at the other end, and the resistance is between the effort and the fulcrum. Always multiply the effort force and do not change its direction.

28. Third Class Levers Fulcrum is at one end of the lever, resistance at the other end, and the effort force is applied between the fulcrum and the resistance. Always multiply distance and speed without changing the direction of the effort force.

29. Mechanical Advantage = Effort Arm / Resistance Arm Mechanical Advantage = Effort Distance / Resistance Distance Mechanical Advantage = Resistance Force / Effort Force

30. If we want to lift a 120 pound rock with a lever that gives us a mechanical advantage of 12, how much force do we have to exert under ideal conditions (without friction)? 10 pounds

31. If we wanted to lift this rock 5 feet, over what distance would we have to exert this force? 60 feet

32. Wheel and Axle – Basically, a circular lever. Axis of rotation is fulcrum. Axle and large wheel correspond to the arms.

33. Mechanical Advatange= Input Radius / Output Radius

34. A bicycle wheel has an input radius of 12 inches, and an output radius of 4 inches. What is the mechanical advantage of the wheel and axle?

35. Pulley – A simple machine consisting of a grooved wheel over which a rope or cable passes.

36. Fixed Pulley – A pulley that does not move with resistance. Does not multiply effort force, merely reverses it.

37. Movable Pulley – A pulley that is attached to the resistance and moves with it. Allows the effort force applied (discounting friction) to be only half of the resistance force.

38. Block and Tackle Pulley – A combination of one or more fixed pulleys and one or more movable pulleys. Movable pulleys are used to multiply the effort force while the fixed pulleys are used to change the direction of the effort force. Mechanical Advantage = Number of rope segments supporting the resistance.

39. Inclined Plane – A sloping platform that enables us to move an object to a higher position without having to lift it straight up. Mechanical Advantage = Effort Distance / Resistance Distance

40. If a block and tackle pulley system has 8 segments of ropes supporting a log, what is the mechanical advantage of the pulley system? 8

41. Wedge – A special form of an inclined plane. Modifies force and changes its direction to the sides. Mechanical Advantage = length / thickness.

42. John uses a 10 inch long ax head that is 4 inches thick. What is the mechanical advantage of the wedge. 4

43. Screw – Spiral form of an inclined plane. Apply force in the direction of their axis as they are turned.

44. Pitch – The distance across two of the ridges or thread’s on the screw’s shart. Mechanical Advatange= 2 r / Pitch

45. What is the mechanical advantage of a screw that has a radius of 6 inches and a pitch of 4 inches? 3

46. Efficiency = Work Output / Work Input x 100 %

47. A machine has a work output of 4 joules, and a work input of 5 joules. What is the efficiency of the machine? 80 %