1. Unit 5 - Machines
MACHINES – UNIT 5

2. ANY DEVICE THAT HELPS PEOPLE DO WORK.
DEFINITION OF MACHINE
ANY DEVICE THAT HELPS PEOPLE DO WORK.
IT DOES NOT CHANGE THE AMOUNT OF WORK DONE

3. MACHINES ALSO DON’T CHANGE THE AMOUNT OF WORK NEEDED, SO…
WORK CONSERVATION
MACHINES DO NOT INCREASE THE WORK YOU PUT INTO THEM. THE WORK THAT COMES OUT OF A MACHINE CAN NEVER BE GREATER THAN THE WORK THAT GOES INTO THE MACHINE.
MACHINES ALSO DON’T CHANGE THE AMOUNT OF WORK NEEDED, SO…

4. HOW DO MACHINES MAKE WORK EASIER?
BY CHANGING SIZE OF THE FORCE NEEDED TO DO THE WORK AND THE DISTANCE OVER WHICH THE FORCE IS APPLIED
BY CHANGING THE DIRECTION IN WHICH THE FORCE IS APPLIED

5. SO, WHY DO WE SAY THAT MACHINES MAKE WORK “EASIER”?
THERE ARE 3 WAYS THAT A MACHINE CAN MAKE A TASK “EASIER”.

6. OUTPUT DISTANCE IS LESS
IT CAN MULTIPLY THE SIZE OF THE INPUT FORCE, BUT DECREASE THE DISTANCE OVER WHICH THE FORCE MOVES
OUTPUT DISTANCE IS LESS
THAN INPUT DISTANCE

7. OUTPUT DISTANCE IS MORE THAN INPUT DISTANCE
IT CAN MULTIPLY THE INPUT DISTANCE, BUT DECREASE THE SIZE OF THE FORCE.
OUTPUT DISTANCE IS MORE THAN INPUT DISTANCE

8. 3. IT CAN LEAVE BOTH FORCE AND DISTANCE UNCHANGED, BUT CHANGE THE DIRECTION IN WHICH THE FORCE MOVES.

9. (THIS IS WORK CONSERVATION)
IN OTHER WORDS…MOST MACHINES MAKE WORK EASIER BY MULTIPLYING EITHER FORCE OR DISTANCE - BUT NEVER BOTH. NO MACHINE CAN MULTIPLY BOTH FORCE & DISTANCE!!!
(THIS IS WORK CONSERVATION)

10. THE NUMBER OF TIMES A MACHINE MULTIPLIES THE EFFORT FORCE
MECHANICAL ADVANTAGE
THE NUMBER OF TIMES A MACHINE MULTIPLIES THE EFFORT FORCE
Formula = OUTPUT FORCE
___________________________________________________________
ie. pulleys INPUT FORCE

11. THE MECHANICAL ADVANTAGE TELLS YOU HOW MUCH FORCE IS GAINED BY USING THE MACHINE

12. WHAT ABOUT OTHER MACHINES
FOR INCLINED PLANES:
LENGTH OF INCLINE / HEIGHT OF INCLINE
OR… INPUT DISTANCE / OUTPUT DISTANCE
FOR WHEEL AND AXLES:
WHEEL RADIUS / AXLE RADIUS

13. WORK TRANSFERS ENERGY
MACHINES TRANSFER ENERGY TO OBJECTS ON WHICH THEY DO WORK (INCLUDING YOURSELF)
WHAT’S THE DIFFERENCE IN WORK BETWEEN CLIMBING A MOUNTAIN STRAIGHT UP AND HIKING UP THE GENTLE SLOPE ON THE SIDE?

14. TWO TYPES OF WORK INVOLVED IN USING A MACHINE
WORK INPUT = THE WORK THAT GOES INTO A MACHINE; EFFORT FORCE EXERTED OVER DISTANCE

15. WORK OUTPUT = THE WORK THAT COMES OUT OF A MACHINE; OUTPUT FORCE EXERTED OVER A DISTANCE

16. KEY WORDS FORCE DISTANCE WORK INPUT FORCE INPUT DISTANCE WORK INPUT
OUTPUT FORCE
OUTPUT DISTANCE
WORK OUTPUT

17. WORK EFFICIENCY (%) WORK INPUT FORMULA = WORK OUTPUT
COMPARISON OF WORK OUTPUT TO WORK INPUT
THE CLOSER WORK OUTPUT IS TO WORK INPUT, THE MORE EFFICIENT THE MACHINE.
NO MACHINE IS EVER 100% EFFICIENT…WHY?
FORMULA = WORK OUTPUT
x 100%
WORK INPUT

18. MACHINE EFFICIENCY PROBLEMS
WORK OUTPUT / WORK INPUT X 100
YOU DO 4000J OF WORK USING A SLEDGE HAMMER. THE SLEDGE HAMMER DOES 3000J OF WORK ON THE SPIKE. WHAT IS THE EFFICIENCY OF THE SLEDGE HAMMER?
3000J / 4000J = .75 X 100% = 75%

19. YOU DO 250J OF WORK USING AN INCLINED PLANE
YOU DO 250J OF WORK USING AN INCLINED PLANE. THE INCLINED PLANE DOES 100J OF WORK ON THE OBJECT. WHAT IS THE EFFICIENCY?
100J / 250J = .4 X 100 = 40%

20. REMEMBER…MACHINES CAN MULTIPLY FORCE, BUT NOT WORK.
YOU CAN’T GET MORE WORK OUT OF A MACHINE THAN YOU PUT INTO IT EVEN IF YOU DO GET MORE FORCE

21. INCREASING EFFICENCY
ONE WAY TO INCREASE EFFICIENCY OF A MACHINE IS TO REDUCE FRICTION
HOW CAN YOU INCREASE THE EFFICENCY OF A BIKE?

22. Unit 5 - Machines

23. EFFORT
DEFINITION: THE FORCE YOU APPLY TO THE LEVER/MACHINE.

24. RESISTANCE THE FORCE THAT YOU AND THE MACHINE ARE WORKING AGAINST.
ALSO REFERRED TO AS THE LOAD.
FOR EXAMPLE, WHEN USING A WHEELBARROW TO MOVE DIRT, THE WEIGHT OF THE DIRT IS THE RESISTANCE.

25. THE FIXED PIVOT POINT OF A LEVER.
FULCRUM
THE FIXED PIVOT POINT OF A LEVER.
Fulcrum

26. L E V R

27. A RIGID BAR THAT’S FREE TO MOVE ABOUT A FIXED POINT CALLED A FULCRUM
LEVER
A RIGID BAR THAT’S FREE TO MOVE ABOUT A FIXED POINT CALLED A FULCRUM
Examples: Shovel, nutcracker, seesaw, crowbar, tweezers, fishing pole, door, etc

28. THE PARTS OF THE LEVER WHERE IS THE FULCRUM?
WHERE IS THE EFFORT OR FORCE?
WHERE IS THE RESISTANCE?

29. THREE CLASSES OF LEVERS
THERE ARE THREE CLASSES, OR TYPES, OF LEVERS
FIRST-CLASS
SECOND-CLASS
THIRD-CLASS
A LEVER’S CLASS IS DETERMINED BY WHAT IS IN THE MIDDLE: THE FULCRUM, THE RESISTANCE, OR THE EFFORT.

30. FIRST CLASS LEVERS THE FULCRUM IS LOCATED BETWEEN
THE EFFORT AND THE RESISTANCE.
Load
Effort

31. SECOND CLASS LEVERS THE RESISTANCE IS LOCATED BETWEEN
THE FULCRUM AND THE EFFORT.

32. THIRD CLASS LEVERS
THE EFFORT IS BETWEEN THE RESISTANCE AND THE FULCRUM.

33. PLEASE TURN TO PAGE 155 IN YOUR TEXTBOOK
Unit 5 - Machines
PLEASE TURN TO PAGE 155 IN YOUR TEXTBOOK
FIRST-CLASS LEVER: FULCRUM IS IN THE MIDDLE.
SECOND-CLASS LEVER: RESISTANCE IS IN THE MIDDLE.
THIRD-CLASS LEVER: EFFORT IS IN THE MIDDLE.

34. WHAT CLASS OF LEVER IS THIS?

35. WHAT CLASS OF LEVER IS THIS?

36. FIRST-CLASS
X force/ distance
SECOND-CLASS
X force/ distance
THIRD-CLASS
force / X distance

37. How can you affect the mechanical advantage of a lever?
If you move the position of the fulcrum & push down on the lever, the box becomes easier to lift. But in order for it to become easier you have to push the lever down a great distance of 1.5 meters to lift the box up a short distance of .5 meters at the other end of the lever. The task becomes easier because it’s a small force but over a large distance which is converted into a large force over a short distance.

38. WHEEL & AXLE
MADE UP OF TWO CIRCULAR OBJECTS OF DIFFERENT SIZES WITH THE WHEEL AS THE LARGER OBJECT

39. WHAT HAPPENS IF THE FORCE IS APPLIED TO THE AXLE?
WHEEL & AXLE
WHEEL IS LARGER SO IT TRAVELS A GREATER DISTANCE. THE FORCE APPLIED TO THE WHEEL IS MULTIPLIED WHEN IT’S TRANSFERRED TO THE AXLE, WHICH TRAVELS A SHORTER DISTANCE.
WHAT HAPPENS IF THE FORCE IS APPLIED TO THE AXLE?

40. A ROPE, BELT, OR CHAIN WRAPPED AROUND A GROOVED WHEEL
PULLEY
A ROPE, BELT, OR CHAIN WRAPPED AROUND A GROOVED WHEEL

41. PULLEY FIXED PULLEYS ONLY CHANGE THE DIRECTION OF A FORCE
MOVABLE PULLEYS CHANGE THE AMOUNT OF THE FORCE
PULLEY SYSTEMS MAY CHANGE THE DIRECTION OF A FORCE AND THE AMOUNT OF THE FORCE

42. INCLINED PLANE
A FLAT, SLANTED SURFACE

43. INCLINED PLANE WHERE IS THE INPUT DISTANCE?
WHERE IS THE OUTPUT DISTANCE?

44. INCLINED PLANE
MULTIPLIES THE INPUT FORCE, AND DECREASES THE DISTANCE OVER WHICH OUR FORCE IS EXERTED.

46. IT’S AN INCLINED PLANE THAT MOVES
WEDGE
IT’S AN INCLINED PLANE THAT MOVES

47. A SMALL EFFORT FORCE IS ABLE TO OVERCOME A LARGE RESISTANCE FORCE.
WEDGE
A SMALL EFFORT FORCE IS ABLE TO OVERCOME A LARGE RESISTANCE FORCE.

48. IT’S AN INCLINED PLANE WRAPPED AROUND A CYLINDER TO FORM A SPIRAL
SCREW
IT’S AN INCLINED PLANE WRAPPED AROUND A CYLINDER TO FORM A SPIRAL

49. SCREW IT ROTATES & WITH EACH TURN MOVES A CERTAIN DISTANCE.
IT MULTIPLIES THE EFFORT FORCE BY ACTING THROUGH A LONG DISTANCE.

50. MECHANICAL ADVANTAGE OF SIMPLE MACHINES
Formula = OUTPUT FORCE
___________________________________________________________
INPUT FORCE
IF A MACHINE DECREASES THE FORCE YOU USE YOU USE TO DO WORK, YOU CAN FIND THE “IDEAL” MECHANICAL ADVANTAGE WITHOUT KNOWING THE INPUT AND OUTPUT FORCES. BUT, YOU MUST ASSUME THE SIMPLE MACHINE IS 100% EFFICIENT

51. WH
IMA - INCLINED PLANE
TO FIND THE IDEAL MECHANICAL ADVANTAGE YOU DIVIDE:
LENGTH OF THE INCLINE
HEIGHT OF THE INCLINE
l IMA = h

52. IMA – WHEEL & AXLE TO FIND THE IDEAL MECHANICAL ADVANTAGE YOU DIVIDE:
RADIUS OF THE INPUT
RADIUS OF THE 0UTPUT
R (in) IMA =
R (out)

53. IMA – LEVERS TO FIND THE IDEAL MECHANICAL ADVANTAGE YOU DIVIDE:WH
IMA – LEVERS
TO FIND THE IDEAL MECHANICAL ADVANTAGE YOU DIVIDE:
DISTANCE FROM THE INPUT FORCE TO THE FULCRUM
DISTANCE FROM THE OUTPUT FORCE TO THE FULCRUM
d (in) IMA =
d (out)

54. A COMBINATION OF TWO OR MORE SIMPLE MACHINES
COMPOUND MACHINE
A COMBINATION OF TWO OR MORE SIMPLE MACHINES

55. CONNECT TWO OR MORE WHEEL AND AXLES TOGETHER BY USING TEETH
GEARS
CONNECT TWO OR MORE WHEEL AND AXLES TOGETHER BY USING TEETH

56. A THIRD GEAR CAN BE ADDED TO MAKE THEM MOVE IN THE SAME DIRECTION
GEARS
TWO GEARS THE SAME SIZE AND NUMBER OF TEETH WILL TURN THE SAME SPEED, BUT OPPOSITE DIRECTIONS
A THIRD GEAR CAN BE ADDED TO MAKE THEM MOVE IN THE SAME DIRECTION

57. GEARS THE GEAR THAT TURNS ANOTHER GEAR EXERTS THE INPUT FORCE
THE GEAR THAT IS TURNED EXERTS THE OUTPUT FORCE

58. GEARS
A DIFFERENCE IN SPEED BETWEEN TWO GEARS (CAUSED BY A DIFFERENCE IN SIZE AND DISTANCE EACH TURNS THROUGH) PRODUCES A CHANGE IN FORCE

59. MECHANICAL ADVANTAGE OF COMPOUND MACHINES
THE M.A. OF A COMPOUND MACHINE IS EQUAL TO THE SUM OF THE M.A. OF ALL THE SIMPLE MACHINES THAT MAKE UP THE COMPUND MACHINE

60. WHAT ARE EXAMPLES OF COMPUND MACHINES YOU USE?
COMPOUND MACHINES
WHAT ARE EXAMPLES OF COMPUND MACHINES YOU USE?