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-   -   Related rates (https://www.askmehelpdesk.com/showthread.php?t=150446)

  • Nov 10, 2007, 05:46 AM
    galactus
    Related rates
    Few calc problems are posted on this site. For us mathophiles, here's a related rates problem if anyone would like to have a go:

    A cylindrical beaker has radius r and height h. Water is pouring out as the beaker is tilted. Find a formula that relates the rate of change of the volume of water in the beaker and the rate of change of the angle the beaker makes with the vertical.
  • Nov 10, 2007, 10:49 AM
    jehan60188
    this isn't a very difficult question as far as related rates go, but finding the volume of the liquid is pretty complicated
    Inclined cylinder volume calculation for tanks and pipes. here's a discussion on that
    when you do find the volume, just differentiate with respect to theta
  • Nov 10, 2007, 03:07 PM
    galactus
    Thanks for that link. That's interesting.

    You're correct, it's not too bad. But here's my solution to the problem:

    If we let, say, d = the depth of the water at the axis of the cylinder, then







    Then we have:















    r and h are constant, so differentiating wrt theta:




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