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Science 8

Unit D

Lesson 3

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Analyze a mechanical device, by:

  • describing the overall function of the device

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  • describing the contribution of individual components or subsystems to the overall function of the device

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  • identifying components that operate as simple machines

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Watch until 4 min mark

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Video For Each Simple Machine

Pulleys

Inclined Plane

Levers

Wheel and Axle

Wedge

Screw

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Types of Levers

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COULDN’T SAY IT BETTER MYSELF:

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Simple machines can

  • multiply the force that you apply,
  • or change the direction of the force,
  • but there is a cost.

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The force that you apply has to move more than the load does.

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The 4 main effects of simple machines

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The 4 main effects of simple machines.

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1.to change the force

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2.to multiply the force

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3.increasing and decreasing the speed

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4.transferring force.

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Scavenger Hunt KEY

  1. B
  2. A
  3. 100 Joules
  4. True
  5. C
  6. 1. Wedge, 2. Inclined Plane, 3. Pulley, 4. Screw, 5. Lever, 6. Wheel and Axle
  7. B
  8. D
  9. A
  10. B
  11. Energy is the ability to apply a force to perform work. Work is applying a force to move something, which requires energy
  12. Both can be used to lift an object. A wheel and axle is also used to move objects across large distances

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Scavenger Hunt KEY

13. Well: Wheel and Axle; Shovel: Wedge; Slide: Inclined Plane

14. A wheelbarrow is a lever and a wheel and axle. The wheelbarrow body is like the lever that helps you lift and carry a load. The wheel helps you move the load.

15. Wedge and Lever

16. Pros: Reduces effort to perform work

Cons: Increases the distance you have to perform work

17. Wheel and axle

18. It would raise it

19. Pull the rope down

20.Increase the number of threads or twists on the screw

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Scavenger Hunt KEY

21. A

22. C

23. A = Load B = Effort

24. C

25. Most often a simple machine reduces the force needed to do work but increases the distance that force is applied

26. False (3rd class levers do not provide mechanical advantage)

27. A: 3 B:2 C:1

28.C

29. W = FxD

W = 25N x 100m

W = 2500 J

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Scavenger Hunt KEY

30. P = W / t

P = 120 J / 2 s

P = 60 Watts

31. Input force is the force you apply to a simple machine. Output force is the work performed by the machine

32. The rate of doing work equals the rate of using energy

33. The mechanical advantage increases.

34. You will have to pull the rope twice as far (20m) to lift the box 10 meters.

35. The force decreases but the distance you must apply the force increases.

36. The input force is closer to the fulcrum than the load. There is no mechanical advantage but the distance to perform the work is shorter/smaller