1 / 131

Science 8 Unit D: Mechanical Systems

Science 8 Unit D: Mechanical Systems. Topic 1.1 Learner Outcomes. Investigate and provide examples of mechanical devices used in the past to meet particular needs Illustrate how a common need has been met in different ways over time Identify components that operate as simple machines.

sharons
Download Presentation

Science 8 Unit D: Mechanical Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Science 8 Unit D: Mechanical Systems

  2. Topic 1.1 Learner Outcomes • Investigate and provide examples of mechanical devices used in the past to meet particular needs • Illustrate how a common need has been met in different ways over time • Identify components that operate as simple machines

  3. Section 1.1 – Simple Machines – Meeting Human Needs • Early machines were very simple devices. • EX. Levers were used to pry rocks from the ground. • EX. Ramps were used to raise rocks to build walls. • First machines used humans or animals as sources of energy.

  4. Class Discussion • What were the items in figure 1.1 use for historically? • How do the items work? • What needs were they designed to meet? • What is the approximate time period each were used in?

  5. Moving Water Historically • No pumps to move water, so people used gravity. • Water stored in raised tanks, gravity caused it to move through the pipes and to the community. • Water and moved to raise tanks by water wheels (sakia) • a series of buckets attached to a long rope, which is draped over a large wheel •  Animals turned the wheel, which raised the buckets of water.

  6. Sakia

  7. Moving Water Historically • Archimedes made a more efficient way by developing the Archimedes screw. • Moves water by moving a screw. • Still used today with a grain auger.

  8. Archimedes Screw

  9. Simple Machines • Simple machines– tool or device made up of one basic machine • Every machine performs at least one of these functions. • The machine may: • Change the direction of a force • Multiply the speed or distance • Transfer the force from one place to another • Multiply force

  10. Simple Machines • Make a chart like the one provided in the book on page 261 until it in as we go.

  11. Your chart should look something like this (page 261)

  12. 1. Lever • Rigid bar or plank that rotates around a fixed point called a pivot or fulcrum. • ADV: lever are used to reduce force needed to carry out a task • DISADV: to move a large load with a lever, you must move a greater distance than the load does

  13. Lever

  14. Lever Video

  15. 3 Types of Levers • First class lever – fulcrum is between the load and the point where effort is exerted • EX. See saw, pry bar • Second class lever – load is between the effort and the fulcrum (fulcrum and the effort are at the opposite ends of the lever) • EX. Wheelbarrow • Third class lever – effort between the load and the fulcrum • EX. Arm, hammer

  16. 3 Types of Levers GOOD FOR: Moving heavy loads EX. Crowbars and pliers GOOD FOR: Lifting heavy objects EX. Wheelbarrow GOOD FOR: Gaining speed EX. Hammer, your arm

  17. Three Classes of Lever Video

  18. 2. Inclined Plane • Makes it possible to lift heavy objects using smaller force • Also called a ramp • ADV: Uses a much smaller amount of force than if you did not use the ramp. • DISADV: Have to exert a force over a larger distance • DISADV: Often only used over small inclines – the steeper the ramp, the harder it is to control the object. • EX. Wheelchair access ramps

  19. Inclined Plane

  20. Inclined Plane Video

  21. Inclined Plane Online Gizmo • LearnAlberta • Username: LA389 • Password: 9489 • Ant on a Slant • Try activity and answer the multiple choice questions afterwards. • Give Ms. Benard your score.

  22. 3. Wedge • Similar to the inclined plane but used in a different way • Wedge machine is forced into an object. • ADV: Wedge increases the force that you apply on the object. • Press on wide edge of wedge to exert a force on the narrow end to split an object apart • DISADV: Wedge only pushes object apart (unlike a ramp which can be used to move objects up or down) • EX. Knives and axes

  23. Wedge

  24. Wedge Video

  25. 4. Screw • Cylinder with the groove cut in a spiral on the outside. • Helps to increase the force you use • Penetrates materials was little force • Used to convert rotational motion to linear motion (grain auger) • Moves objects slowly.

  26. Screw

  27. Screw Video

  28. 5. Pulley • Consists of wire, rope or cable moving on grooved wheel • Pulleys made of one or more wheels • Pulleys can be fixed in place or moveable • Pulley systems can be used to: • Reduce effort • Increase speed • Change direction

  29. Pulley

  30. Pulley Video

  31. Pulley Online Gizmo • LearnAlberta • Username: LA389 • Password: 9489 • Pulleys (Piano, Armchair) • Try activity and answer the multiple choice questions afterwards. • Give Ms. Benard your score.

  32. 6. Wheel and Axel • Combination of two wheels of different diameters that turn together • A longer motion on the wheel produces a shorter more powerful motion at the axel • Force advantage • Must turn more on the larger wheel to apply the force • EX. Steering wheel and steering column

  33. Wheel and Axel • If force is applied to the axle and the load on the wheel, you can increase the speed. • Speed advantage • Must apply a large force to move the load • EX. Bicycle

  34. Wheel and Axel

  35. Wheel and Axel Video

  36. Wheel and Axel Online Gizmo • LearnAlberta • Username: LA389 • Password: 9489 • Wheel and Axel • Try activity and answer the multiple choice questions afterwards. • Give Ms. Benard your score.

  37. Video Review Quiz http://www.msichicago.org/fileadmin/Activities/Games/simple_machines/

  38. Assignment • Complete Questions 1-4 on page 268

  39. Topic 1.2 Learner Outcomes • Describing the overall function of the device • Describing the contribution of individual components or subsystems to the overall function of the device

  40. Section 1.2 – The Complex Machine • Complex machines– a system where simple machines all work together • System – group of parts that work together to perform a function • Usually a complex machine • EX. Bicycle • Subsystem– group of parts that performed specific functions within a system • Usually a simple machine • EX. Pedal on the bicycle (lever)

  41. Do give it a try, page 271

  42. Complex machines move objects by transferring energy from one source to the object. • Subsystems that transfer force are: • Linkages • Transmissions

  43. 1. Linkages • Belt or chain to directly transfer energy from energy source to an object • EX. Bicycle chain • You (the energy source) move your energy to the bicycle wheels (objects you want to move) by pedaling. Pedaling moves the chain which moves the bike tires. • Energy source Linkage  Object to move • High tension belts can also be used • EX. In a car motor

  44. Linkages

  45. 2. Transmissions • Special types of linkage • Transfer the energy from the engine to the wheels in large vehicles such as cars and trucks • Used to move much larger loads (transfers more force) • Contains many gears • Low gear = move slowly • High gear = moves quickly

  46. Transmissions

  47. Gears • Pair or series of wheels with teeth interlinked • When they rotate, one gear wheel transfers turning motion and force to the other. • Larger gearwheel moves more slowly than the smaller gearwheel, but it rotates with a greater force. • EX. Car • Gears also used to change the direction of motion • EX. Egg beater • Gears are important because they control the transfer of energy from one source to another. • EX. Rider to the bike tires • EX. Car engine to car tires

More Related