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moongazer Group Title

The speed of a car is 80 miles per hour. Find the radius of the car wheels in inches if the car makes 300 rev/min.

  • 2 years ago
  • 2 years ago

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  1. moongazer Group Title
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    I got r=44.82 inches is it correct?

    • 2 years ago
  2. amistre64 Group Title
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    how many revolutions per hour does it make?

    • 2 years ago
  3. moongazer Group Title
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    5 rev per hour

    • 2 years ago
  4. amistre64 Group Title
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    really? it does 300 revs in one minute; how can it do way less revs in one hour?

    • 2 years ago
  5. amistre64 Group Title
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    300*60 ...

    • 2 years ago
  6. moongazer Group Title
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    sorry for that I interchanged it :) 18000 per hour

    • 2 years ago
  7. amistre64 Group Title
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    18000 revs in one hour put to the ratio of 80 miles 18000/80 is our next step i believe

    • 2 years ago
  8. amistre64 Group Title
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    of if we knew how many inches 80 miles was we could go more directly to an answer ....

    • 2 years ago
  9. moongazer Group Title
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    why did you made it into ratio?

    • 2 years ago
  10. amistre64 Group Title
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    becasue that is what it is: 18000 revs = 80 miles i spose since we want to know how far 1 rev takes us its better to make the rev side equal to 1 tho divide both sides by 18000

    • 2 years ago
  11. amistre64 Group Title
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    1 rev = the circumference of the wheel

    • 2 years ago
  12. moongazer Group Title
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    sorry I got confused :)

    • 2 years ago
  13. amistre64 Group Title
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    if we convert 80 miles to inches; then we know how many inches 1 rev is; so we would know how many inches the circumference of the wheel is knowing circunference is equal to 2pi*radius; we solve for the radius r = C/2pi

    • 2 years ago
  14. moongazer Group Title
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    Sorry, but I am really confused with your method. :) I did angular and linear speed with this one.

    • 2 years ago
  15. amistre64 Group Title
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    google says: 1mile=63360inches multiply both sides by 80 we get 80 miles = 5 068 800 inches 18000 revs = 5 068 800 inches divide both sides by 18000 to get 1 revolution 5 068 800/ 18000 = 281.6 281.6 inches is our circumference therefore, using what i posted up above; radius = 281.6/(2pi)

    • 2 years ago
  16. amistre64 Group Title
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    i did the same, i converted angular (rpm) into linear (miles, inches)

    • 2 years ago
  17. amistre64 Group Title
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    of course i get about a wheel that is about 7 feet in diameter lol

    • 2 years ago
  18. moongazer Group Title
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    brb. i'll try to understand your method. it looks good :) still, I think we got the same answer but different method of getting it.

    • 2 years ago
  19. amistre64 Group Title
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    44.82, yes

    • 2 years ago
  20. moongazer Group Title
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    and I think your method is faster :)

    • 2 years ago
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