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Homework Help: Finding kilograms of water on a spherical planet

  1. Aug 25, 2015 #1
    (Moderators note: moved from technical forums, does not use template)

    How would someone approach this problem?

    Find mass in kg of spherical planet if:
    -71.11% of surface is covered by oceans
    - avg depth of oceans is 12.83 furlongs
    -avg density of water is 1.030 g/mL
    -avg radius of planet is 4,895 miles
    Last edited by a moderator: Aug 26, 2015
  2. jcsd
  3. Aug 25, 2015 #2


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    Do you have an average density for the non-water part of the planet? Or are you just looking for the mass of water on the spherical planet?

    Edit: I see now in the title that you are just looking for the water.

    Step 1, draw a picture.
    Step 2, find the total volume of the sphere from avg. depth to avg. radius.
    Step 3, multiply total volume by % surface that is water.
    Step 4, multiply that volume by density to find mass.
  4. Aug 25, 2015 #3


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    Step 1.5: use consistent units in your calculations. :wink:
  5. Aug 25, 2015 #4


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    When in doubt, google's unit conversion tool is very helpful.
    "convert furlongs to km" returns.
    1 furlong = 0.201168 kilometers.
  6. Aug 25, 2015 #5
    I got 3.518x10^16 kg. Does that sound reasonable?

    Edit: Disregard that I may have found an error in my calculations
    Last edited: Aug 25, 2015
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