3. Lesson 8 Gears and Ratios Click below for animation http://www.dynamicscience.com.au/tester/solutions/hydraulicus/gears1.htm

4. Activity 1 Gears 10 minutes

5. First pair

6. Question 1 How many times do you have to turn the small wheel to make the large one turn twice? How many times do you have to turn the small wheel to make the large one turn twice? 1. Small wheel turns............. 1. Small wheel turns............. (big wheel turns twice) (big wheel turns twice)

7. Question 2 Without doing it, work out how many times the small wheel would turn if you turned the large one once. Without doing it, work out how many times the small wheel would turn if you turned the large one once. 2. Guess small wheel turns............. 2. Guess small wheel turns............. when big wheelturns once when big wheelturns once

8. Question 3 3 Real answer is.............

9. Question 4 4 Ratio is.......... (big wheel : small wheel) 4 Ratio is.......... (big wheel : small wheel)

10. Question 5 5 Turn big wheel 20 times in a minute and the small wheel’s speed is............. 5 Turn big wheel 20 times in a minute and the small wheel’s speed is.............

11. Second pair 1 Small wheel turns............. (big wheel turns twice) 1 Small wheel turns............. (big wheel turns twice) 2 Guess small wheel turns............. when big wheel turns once 2 Guess small wheel turns............. when big wheel turns once 3 Real answer is............. 3 Real answer is............. 4 Ratio is............. (big wheel : small wheel) 4 Ratio is............. (big wheel : small wheel) 5 Turn big wheel 20 times in a minute and the small wheel’s speed is............. 5 Turn big wheel 20 times in a minute and the small wheel’s speed is.............

12. Activity 2 Scale drawing Who likes drawing? I need 2 volunteers. Who likes drawing? I need 2 volunteers. Could you draw a mouse on the board for me? Could you draw a mouse on the board for me? Could you draw an elephant. Next to the mouse. Could you draw an elephant. Next to the mouse. You have 3 minutes.

13. The elephant. Is the drawing of the elephant bigger or smaller than a real elephant? Is the drawing of the elephant bigger or smaller than a real elephant? Why did the artists draw it this way? Why did the artists draw it this way? How much smaller is the drawing than a real elephant? How much smaller is the drawing than a real elephant?

14. The mouse. Is the drawing of the mouse bigger or smaller than a real elephant? Is the drawing of the mouse bigger or smaller than a real elephant? Why did the artists draw it this way? Why did the artists draw it this way? How much bigger is the drawing than a real mouse? How much bigger is the drawing than a real mouse?

15. Activity 2 Scale drawing Are the drawings ‘to scale’? Are the drawings ‘to scale’? Are they both to the same scale? Are they both to the same scale?

16. Human Embryos 6 weeks old life size 12mm

17. 3 months old. Life size 45mm

19. Human Embryos None of them are drawn ‘life size’. Why not? None of them are drawn ‘life size’. Why not? Which drawings have been scaled up (made larger than life)? Which drawings have been scaled up (made larger than life)? Which drawings have been scaled down (made smaller than life)? Which drawings have been scaled down (made smaller than life)?

20. We can say more about how each of the drawings has been scaled up or down if we take some measurements. We can say more about how each of the drawings has been scaled up or down if we take some measurements.

21. Age of embryo Drawing size (mm) Real size (mm) Ratio of drawing : real Scale 6 weeks 3 months 9 months

22. Age of embryo Drawing size (mm) Real size (mm) Ratio of drawing : real Scale 60 60 135 135 90 90 12 12 45 45 360 360 5:1 5:1 3:1 3:1 1:4 1:4 x5 x5 x3 x3 x1/4 x1/4 6 weeks 3 months 9 months

23. Work with the other people in your group to complete these sentences: Work with the other people in your group to complete these sentences: When we draw a picture or a map to scale we would do it by............. When we draw a picture or a map to scale we would do it by............. The word ratio means............. The word ratio means............. It is useful to be able to work out scales and ratios because............. It is useful to be able to work out scales and ratios because.............

24. More thinking about Gears and Ratios Work as a group doing the questions on “more thinking about gears and ratios. Work as a group doing the questions on “more thinking about gears and ratios.

25. Barbie Doll Mattel manufactured the first Barbie Doll in 1959. She was 11 1/2 inches tall and was designed with the very distinctive shapely body. Song

26. Barbie Doll How long are her legs in relation to her height? How long are her legs in relation to her height? Legs (Heel to Hip) ______ cm Legs (Heel to Hip) ______ cm Height (Heel to Top of Head) ______ cm Height (Heel to Top of Head) ______ cm What is the doll ratio? ____ to ____ What is the doll ratio? ____ to ____

27. Barbie Doll How long are her legs in relation to her height? How long are her legs in relation to her height? Legs (Heel to Hip) 15 cm Legs (Heel to Hip) 15 cm Height (Heel to Top of Head) 30 cm Height (Heel to Top of Head) 30 cm What is the doll ratio? 1 to 2 What is the doll ratio? 1 to 2

28. Real People How long are your legs in relation to your height? How long are your legs in relation to your height? Legs (Heel to Hip) ______ cm Legs (Heel to Hip) ______ cm Height (Heel to Top of Head) ______ cm Height (Heel to Top of Head) ______ cm What is the real ratio? ____ to ____ What is the real ratio? ____ to ____

29. Whose legs are too long?

30. Give an example where you need to think about scales or ratios outside school. Give an example where you need to think about scales or ratios outside school.