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Homework Help: Beginning physics problem

  1. Aug 23, 2008 #1
    Please help with this problem. I don't understand how you can know a quantity of rainfall over the given city area just by knowing 1.1 cm.

    The problem:
    A heavy rainstorm dumps 1.1 cm of rain on a city 5 km wide and 9 km long in a 2-h period.

    (a)How many metric tons (1 metric ton = 10^3 kg) of water fell on the city? (1 cm^3 of water has a mass of 1 gram = 10^-3 kg.)

    (b)How many gallons of water was this?

    For A, I know that if I can find kg of water, I can find metric tons easily enough. I could find kg by the 1cm=1g=10^-3kg, but I don't know how to find out how much rain was dropped on the city given the dimensions and 1.1 cm. How do you relate these two?


    Last edited: Aug 23, 2008
  2. jcsd
  3. Aug 23, 2008 #2


    User Avatar
    Homework Helper

    Welcome to PF.

    Maybe ask yourself this question?
    Depth of water times area is volume isn't it?

    Looks like you have what you need.
  4. Aug 23, 2008 #3
    so does this mean I should multiply 1.1 cm x 45 km? or should I convert 1.1 cm to 1.1x10^-5 km, and then multiply?

    And then that quantity is my volume of rainfall (in km?)...which I can then relate to cm>grams>kg>metric tons.
  5. Aug 23, 2008 #4
    ok i got it.

  6. Aug 23, 2008 #5


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    Homework Helper

    Yes you do have it.

    Good luck.
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