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moongazer

  • 3 years ago

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.

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  1. moongazer
    • 3 years ago
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    I got r=44.82 inches is it correct?

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

  3. moongazer
    • 3 years ago
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    5 rev per hour

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

  5. amistre64
    • 3 years ago
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    300*60 ...

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

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

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

  9. moongazer
    • 3 years ago
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    why did you made it into ratio?

  10. amistre64
    • 3 years ago
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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

  11. amistre64
    • 3 years ago
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    1 rev = the circumference of the wheel

  12. moongazer
    • 3 years ago
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    sorry I got confused :)

  13. amistre64
    • 3 years ago
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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

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

  15. amistre64
    • 3 years ago
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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)

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

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

  18. moongazer
    • 3 years ago
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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.

  19. amistre64
    • 3 years ago
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    44.82, yes

  20. moongazer
    • 3 years ago
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    and I think your method is faster :)

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