Simple Machines Continued: Gears and Friction



Gears
  1. Explain what gears are. (p. 20)
  2. What materials are gears typically made of? (p. 20)
  3. What are gears typically used for? (p. 20)
  4. List at least four example of real-life machines that use gears.
  5. Explain what a gear train is. Quickly sketch a simple two-gear train. (p.20/figure 5)
  6. Explain what a gear ratio is. (p. 20)
  7. A bicycle is an example of a two-gear train connected by a chain. If your front (driver) gear has 10 teeth, and the follower (back) gear has 50 teeth, how many times must your pedal the front gear around to have the back gear rotate once? Explain how you know. (figure 5)
  8. If your front (driver) gear has 60 teeth, and the follower (back) gear has 15 teeth, how many times will the rear gear rotate when the front gear turns once? Explain how you know. (figure 6)
  9. Fill in the blanks. With a __________ gear ratio, the gear can be turned with less ________ but must go a longer __________. (figure 6a)
  10. Fill in the blanks. With a __________ gear ratio, the gear is turned with more ________ but will allow you to travel farther __________. (figure 6c)
  11. Explain what you should do to make pedalling up a steep hill feel easier. (figure 6a)
  12. Explain what you should do to make when pedalling downhill make the best use of your bike gears. (figure 6c)
  13. Answer making connections question#7 on page 21. (p. 21)



Friction

  1. Explain, in your own words, what friction means and how it is created. (p. 24)
  2. In machines explain how friction leads to less efficiency. (p. 24)
  3. Due to friction, _____________ energy is changed into __________ energy. (p. 24)
  4. Friction can occur between solids, but also between solids moving through fluids. Give one real-world example of this. (p. 24)
  5. Explain why boats are very inefficient. (p. 24)
  6. Describe how Hovercrafts are able to reduce friction. (p. 24/figure 2)
  7. Describe two different things that can be done to reduce the amount of friction in machines and mechanisms. (p. 25)
  8. Give two real-world example of where having friction between two surfaces is actually beneficial. (p. 25)

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