Unit 4

1. Unit 4 Mechanical Systems

2. Unit 4 Topic 1 - Machines

3. Simple Machine • What is a machine? • A device that helps us do work • Easy way to remember this … think farming & crops! • Hand tools • Plow • Horse & Plow • Tractor • Combines

4. Meeting Needs • A most basic human need would be water • How has this changed over time? • Before pumps we used gravity…can you think how? • Romans built aqueducts…how did they work? • First machine was a “sakia”…how did that work?

5. Archimedes • When Archimedes was not trying to kill people with the sun he was actually a pretty helpful person! • Designed The Archimedes Screw • A screw inside of a long tube • One end in water • Other over tank/reservoir/etc… • Screw turns and water rises up tube to top • Comes out the other end • Turns via hand crank • Simple Video of Archimedes Screw in Action

6. Archimedes & da Vinci • Hundreds of years later enter da Vinci • He put some Archimedes screws together • Why? • Lifted water from low to higher and higher location

7. Archimedes Screw Today • Do we still use this idea today? • Absolutely! • Farming Industry • Oil & Gas Industry • Construction Industry

8. Simple Machines • So if a machine is that helps us do work … • …what is a simple machine? • A tool/device made up of one basic machine • There are 6 we are going to cover… • Screw • Pulley • Wheel & Axel • Lever • Inclined Plane • Wedge

9. The Lever • What is it? • Rigid bar/plank that can rotate around a fixed point called a pivot or fulcrum • How do they help? • Reduce the force required to carry out a task

10. The Lever - Categories • First Class Lever • The fulcrum (pivot/rotation point) is between load and the point where effort is exerted • Ex: Scissors, Teeter-Totter (See-Saw)

11. The Lever - Categories • Second Class Lever • The load is between the effort (lift) & the fulcrum • Ex: Wheelbarrow

12. The Lever - Categories • Third Class Lever • The effort (lift) is between the load & fulcrum • Ex: Your arm

13. The Lever – Helpful? • Absolutely! • They provide what is known as a… mechanical advantage which is: • Small effort force to move larger load/object

14. Levers – Do I Get It? • Picture if you will … or simply look at the image below … of a pop can. • The tab of a pop can is this kind of lever. Defend! How do I open?! What lever is that?!

15. Inclined Plane • Inclined plane a.k.a. Ramp • These make it easier/possible to move heavy objects certain distances • While the force required is smaller, the distance is greater! • What about how steep the ramp is? • Steeper = more force • Ex: Loading ramps, wheelchair ramps

16. Wedge • A wedge is forced into an object • Put force on one end to split an object apart at the other end • How? • Increases the force you apply to an object • Can only be used in 1 direction … • …to push objects apart • Ex: Knives

17. Screw • A cylinder with grooves cut in a spiral on the outside • Helps increase the force you use/apply • Can penetrate a material to make a hole/bind together • Convert rotational (spinning) motion to linear (straight) motion

18. Pulley • A material (string, rope, etc…) moving in a grooved wheel • Made up of one or multiple wheels and can be fixed or in motionand/or linked together • Help you lift large objects you could not lift on your own

19. Pulley

20. Wheel & Axle • Combination of 2 wheels of different diameters that turn together • Longer motion on the wheel produces a shorter but more powerful motion at the axle • You have to turn a greater distance (larger wheel) to apply the force

21. Summary…

22. Machines Evolve • As societies changes and grew so did our needs … • Needed bigger building • Needed better access to water • Needed better access to food • Let’s examine the bicycle for example… • How has it changed, evolved?

23. Bicycles

24. Complex Machines • We know simple … so what is a complex machine? • A system in which simple machines all work together • Whoa, wait! What is a system? • A group of parts that work together to form a function! • Look back at the bicycle example? • What simple machines make up a bike? • What is the goal of the system that makes up a bike?

25. Subsystems • Some subsystems in complex machines produce motion – fantastic! • How do we transfer that motion/energy/force? • The subsystem that performs these tasks are called linkages & transmissions with gears being a key player!

26. Linkages • A complex machine moves an object by transferring energy from … • Let’s use bikes again! • What is the energy source? • What is the object that you move? • Linkage is the part that transfers your energy to the back wheel! • The chain is that linkage! Object Energy source

27. Linkages Cont … • What would another example of linkage be? • Gears heads … think under the hood of a car! • Belts! Like a fan belt… takes engine energy to cooling fans! • So linkage forms a direct link between two objects - like two wheels – so when one turns the other turns

28. Linkages Cont … • So back to bikes! • The chain sits on a gear (smaller wheel than the bike wheel) when it rotates … • If one wheel is larger, it will rotate more slowly but with a larger force than the smaller wheel • Fun facts: Chains have less of a chance of slipping than a belt but a belt is more flexible

29. Transmission • Many machines are much more complex than bikes so they need a much more complicated linkage • They are known as transmissions • They function on the same principles as bike gears but contain many, many more pieces and gears of varying sizes and transfer much larger forces

30. Transmission Cont … • Low Gears • Transmission connects a small wheel to a larger wheel • Wheel rotates more slowly than the engine does • Increases the amount of power but reduces speed • High Gears • Transmission connects a large wheel to a smaller wheel • Wheel rotates faster than the engine • Reduces power but increases speed • Gears & Transmissions

31. Gears • Pair of wheels linked together by teeth • When one gear turns the other gear turns with it • The larger gear rotates more slowly but with greater force • The smaller gear rotates quicker but with less force • They can also be used to transfer forced directionally • Egg Beater: Horizontal movement  Vertical • They control the transfer of energy!

32. Gears Driving Gear Driven Gears

33. Gears & Speed • If the driving gear is larger than the driven gear … • When you rotate the larger gear once it rotates the smaller gear several times • Increasing speed of rotation • These are called multiplying gears

34. Gears & Speed • If the driving gear is smaller than the driven gear… • When you rotate the smaller gear once the larger gear does not rotate fully • Decreasing speed of rotation • These are called reducing gears

35. Unit 4 Topic 2 – Mechanical Advantages & Speed Ratios (Here comes the math…)

36. Mechanical Advantage • So what is mechanical advantage? • The amount by which a machine can multiply a force • What does that mean? • It means how much it increasing the effort you put into the machine • Also referred to as the force ratio of the machine

37. Mechanical Advantage • There are 2 specific forces in this process … • Input Force • The force applied to the machine • Output Force • The force the machine applies to the object

38. Mech. Adv. Calculations Output Force = Mechanical Advantage (MA) Input Force Newtons (N) What is Force measured in? =

39. Mech. Adv. Calculations What is the mechanical advantage provided by this pulley system? Input Force 45N Output Force 180N

40. Mech. Adv. Calculations What is the mechanical advantage provided by this lever? Input Force Output Force 200N 1200N

41. Mechanical Advantage • So … when you calculate this type of question you are determining how much your force is being multiplied by the system in order to complete the task

42. Speed Ratio • So we know that a mechanical advantage is the amount by which a machine multiplies a force … • … what is a speed ratio? • Well, speed measures the distance an object travels in a given amount of time • So the measure of how the speed of the object is affected by a machine is called the speed ratio

43. Speed Ratio Calculations Input Distance Speed Ratio = Output Distance Meters (m) Centimeters (cm) What is distance measured in? =

44. Speed Ratio Calculations What is the Speed Ratio of this pulley system? Input Distance 4m Output Distance 1m

45. Speed Ratio Calculations What is the Speed Ratio of this pulley system? Input Distance 25m Output Distance 5m

46. Speed Ratio • So … when you calculate this type of question you are determining the how much faster the input section moves in comparison to the output section

47. Less Force & Greater Distance • So these examples clearly illustrate a very important point … • You do not get something for nothing • What does that mean? • Even though you are able to lift a heavier load the trade off is you have to travel a greater distance in order to do it!

48. Less Force & Greater Distance • Which ramp would you rather push that same piano up? Or? 2m 2m 7m 3.2m

49. Mechanical Advantage What is the Mechanical Advantage of this bike? Input Force 650N Output Force 72N

50. Mech Ad. Less Than 1? • Up to this point it has always been more than 1 … does less than 1 mean it is useless? • No! • So what does it mean? • It means the machine is useful for tasks that do not require a large output force • In this case, the output force causes the rider to move much faster than they would walk