Simple Machines

1. Simple Machines Dennis Papesh Holy Angels School Dayton, Ohio papeshdr@holyangels.cc dpapesh@aol.com

2. The Event • Teams will measure and calculate the IMA, AMA, and Efficiency of various simple machines. • Students will determine the above at four different stations. • The machines may be a) a lever, b) an inclined plane, c) a pulley system, or d) a wheel and axle system.

3. The Event • Any or all of the machines may be enclosed or hidden from the student’s view as long as the student has reasonable access to the input and output connections. • The student may be asked to use the information to solve a problem using the machine in a specific way.

4. The Event • Three of the stations will be single simple machines. • One of the stations will be combinations of machines used in series where students will determine the overall IMA, AMA, and Efficiency. • Non-programmable calculators may be used.

5. Nat’l Competition • Teams will construct the simple machines from materials provided so that their simple machine achieves the target IMA, AMA, and efficiency indicated by the judges. • Teams will then measure and calculate the IMA, AMA, and efficiency of their machines.

6. Nat’l Competition • Teams will be required to draw and label their set-up. • At the combination station, teams will only be required to determine the IMA, AMA, and efficiency. No construction required as the station will be set up by the judge. • Application and extension questions may be asked at any or all stations.

7. What is a simple machine? • A machine is anything that changes the size or direction of forces used in doing work • or • A device which multiplies or divides force • It is a ‘simple’ machine because we are only using one at a time • Otherwise, it would be a compound machine

8. A machine makes work easier by changing at least one of three factors • The amount of force you exert, or • The distance over which you exert the force, or • The direction in which you exert the force.

9. What is “mechanical advantage” ? • In simple terms, the mechanical advantage is the number of times a machine increases a force exerted on it.

10. What is the IMAorIdeal Mechanical Advantage ? • The IMA is the mechanical advantage (MA) a machine would have if no other forces, such as friction, are acting upon the machine. • It is the MA of a machine operating at 100% efficiency

11. What is efficiency ? • The efficiency of a machine compares the work output to the work input. • The less friction there is, the closer the output work is to the input work. • It is always expressed as a percent. • The higher the percent, the more efficient the machine is.

12. Efficiency Efficiency = AMA X 100 IMA

13. Calculating efficiency • Efficiency = Work Output Work Input 100 X

14. Force / Newtons • Force is calculated in Newtons • To convert from mass to Newtons Mass in kg x 9.8m/s/s (which is the acceleration due to gravity on earth) 235 g = .235 kg .235 kg x 9.8m/s/s = 2.303 N

15. What are the simple machines? • Wedge • Screw • Inclined Plane • Pulley and Block and Tackle • Wheel and Axle • Lever • 1st class, 2nd class, 3rd class

16. The Wedge • Yes, I know, the rules do not list the wedge as one of the testable machines. • Will I teach my students how to work with the wedge? • Yes, indeed • Mistakes are sometimes made in event test preparations.

17. The Wedge(Two inclined planes back to back) Output distance Input distance Input distance Output distance IMA =

18. The Screw • Yes, I know, the rules do not list the screw as one of the testable machines. • Will I teach my students to work with this machine? • Yes • Remember, mistakes are sometimes made.

19. Screw • Inclined plane wound around a tapered cylinder. • The longer the inclined plane, the less effort, but • The greater distance over which the effort must be applied. • We have to turn the screw more times but with less effort.

20. The Screw Circumference pitch • IMA = 2πr pitch IMA =

21. The Screw • Pitch is the distance between threads. pitch

22. The Screw • The circumference is not necessarily the circumference of the screw. • It is usually the circumference of the device used to turn the screw. • For example, the circumference of the handle of the screwdriver, or • The circumference of the circle described by the handle of a brace and bit.

23. The Screw • Circumference of circle described as handle rotates • Distance between threads (pitch)

24. The Inclined Plane(Ramp) Input distance Output distance Input distance Output distance Length of incline Height of incline IMA = IMA = or

25. Inclined Plane • IMA = 2 m 1 m Length of incline Height of incline 2 m 1 m = = 2

26. Inclined Plane • IMA = 10 m 2 m Input distance Output distance 10 m 2 m = = 5

27. AMA by F(out)/F(in) • AMA can be calculated by dividing the force out (often the weight of the object) by the force in. • AMA = resistance force/effort force • Inputting 3 Newtons and lifting 6 Newtons gives you an AMA of 2. • F(out)/F(in) = 6N/3N = 2

28. The Pulley • IMA = 1 • Only one rope supporting mass (B) • Advantage is you can use body weight to help lift mass. A B

29. The Pulley • IMA = 2 • Two ropes supporting mass (A) and (B) A B

30. The Block and Tackle • The block and tackle is the use of more than one pulley to increase mechanical advantage.

31. The Block and Tackle • IMA = 3 • 3 ropes supporting weight. • B, C, and D • You must pull the rope 3 units down for every one unit the mass rises. B D A C

32. The Wheel and Axle Radius of outer circle Radius of inner circle IMA =

33. IMA of a Wheel and Axle • IMA = 5 cm 1 cm Outer radius Inner radius 5 cm 1cm = = 5

34. Wheel and Axle • What if this doesn’t loosen the bolt?

35. Wheel and Axle • We get a larger wrench which has a greater wheel radius. • Or we put a piece of pipe over the end and break off the head of the bolt.

36. IMA by D(in)/D(out) • IMA, especially on wheel and axles, pulleys, or block and tackle set-ups can be calculated by dividing the effort distance ((D(in)) by the load distance ((D(out)). • Effort moves 6 cm and load moves 2 cm • IMA = D(in)/D(out) = 6 cm / 2cm = 3

37. IMA v. AMA • IMA is calculated using distance • Input 10m / Output 2m = IMA of 5 • AMA is calculated using force or mass • Output 500N / Input 100 N = AMA of 5 • Both are pure numbers (no units)

38. The Lever • 1st Class (LFE) Effort Fulcrum Load

39. The Lever • 2nd Class (FLE) Effort Load Fulcrum

40. The Lever • 3rd Class (FEL) Load Effort Fulcrum

41. IMA of 1st Class Lever Load Distance • IMA = Effort Distance Effort Distance Load Distance

42. IMA of a 1st Class Lever 16 cm 8 cm = Effort distance Load distance 16 cm 8 cm Effort Distance Load Distance = 2 IMI =

43. IMA of a 1st Class Lever 2 cm 24 cm • IMA = 24 cm 2 cm Effort Distance Load Distance = = 12

44. IMA of a 2nd Class Lever • IMA = Load Distance Effort Distance Effort Distance Load Distance

45. IMA of a 2nd Class Lever • IMA = 30 cm 50 cm Effort Distance Load Distance 50 cm 30 cm = = 1.67

46. IMA of a 2nd Class Lever • IMA = 10 cm 50 cm 50 cm 10 cm Effort Distance Load Distance = 5 =

47. IMA of a 3rd Class Lever • IMA = Effort Distance Load Distance Effort Distance Load Distance It will be less than 1 You gain distance or speed rather than less effort

48. IMA of a 3rd Class Lever • IMA = 10 cm 50 cm Effort Distance Load Distance 10 cm 50 cm = = 0.2

49. IMA of all levers (The IMA of all levers can also be calculated by dividing the distance the effort moves divided by the distance the load moves.)

50. Problem 1 10 cm • IMA = 9 (effort distance / load distance) • If effort (input) is 500N, what is the maximum weight (output) which could be lifted. • 500 N x 9 (IMA) = 4500 N 90 cm