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Homework Help: Intro. Physics: scaling problem

  1. Sep 8, 2004 #1
    I am having dificulty with this homework problem. It doesn't seem to give me enough information. I am asked to find the volume and surface area of an object of unknown volume and shape. Here is the problem:

    A sculptor builds a model for a statue of a terrapin to replace Testudo (go UMD!). She discovers that to cast her small scale model she needs 2kg of bronze. When she is done, she finds that she can give it two coats of varnish. the final statue is supposed to be 5 times as large as the model in each dimension. How much bronze will she need? How much varnish should she buy?

    I tried tackleing the problem by assuming that the professor wanted me to look up the density of bronze (for which I found many different types of bronze and therefore many different densities possible) in order to calculate the volume.

    I used the value that bronze's density was 8000kg/m^3 and calcluated that the final sculpture would need 250kg of bronze. Now I am unsure of how to figure out the surface area of the sculpture with what I know. Can someone give me some insight?

    Hopefully my way of tackleing the volume portion of the problem was correct.

  2. jcsd
  3. Sep 8, 2004 #2


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    The density of bronze is not important!

    The height, width and depth of the statue will be 5 times greater.

    The volume of the statue will be ___ times greater.

    The surface are of the statue will be ___ time greater.
  4. Sep 8, 2004 #3
    If the height, width, and depth are all 5 times greater than I know that the volume would be 125 times greater but how do I relate that to the surface area?
  5. Sep 8, 2004 #4


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    The surface area of a cube whise edges have a length of 'l' is 6l^2.

    The surface area of a sphere whose radius is r is 4pi*r^2.

    The surface area of a cyclinder whose radius is r and height is h is: 2pi*r^2 + 2pi*r*h

    What does increasing all their dimensions by 5 do to their surface area?
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