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sweett2639

You're filling a water balloon with a spherical shape. If the water is coming in at 4 cubic inches per second, how fast is the radius changing when the volume is 200 cubic inches? (answer: 0.0241 in/sec)

  • one year ago
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  1. baldymcgee6
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    |dw:1351471895315:dw|

    • one year ago
  2. baldymcgee6
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    @sweett2639 do you follow?

    • one year ago
  3. sweett2639
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    \[v= \frac{ 4 }{ 3 } \pi r ^{3}\]i understand that the volume of a sphere is and that\[\frac{ dv }{ dt } = 4 inches ^{3}/\sec\] but not much more than that

    • one year ago
  4. baldymcgee6
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    |dw:1351472335325:dw|

    • one year ago
  5. sweett2639
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    so you set 200 equal to v and moved the equasion around so that r is 3.628

    • one year ago
  6. baldymcgee6
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    |dw:1351472455417:dw|

    • one year ago
  7. baldymcgee6
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    Right, we know that the volume is 200 in^3 at the moment of interest, therefore we can find what the radius of the sphere is at that moment

    • one year ago
  8. baldymcgee6
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    |dw:1351472567598:dw|

    • one year ago
  9. sweett2639
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    everytime i try to calculate r, i get the wrong number

    • one year ago
  10. baldymcgee6
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    http://www.wolframalpha.com/input/?i=4%2F%284*pi*%283.628%29%5E2%29 just make sure you type it into the calc correctly.

    • one year ago
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