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Homework Help: Having a problem with a fairly early Physics with Calculus 1 problem

  1. Jan 15, 2006 #1
    Hi all, been a while since I posted here needing homework help but it's a new semester and I'm already stumped (much to my shame :shy: ) Anyway, I am presented with the following problem:

    Gold, which has a mass of 19.32 g for each cubic centimeter of volume, is the most ductile metal and can be pressed into a thin leaf or drawn out into a long fiber. (a) If 9.000 oz of gold, with a mass of 27.63 g/oz, is pressed into a leaf of 1.000 mm thickness, what is the area (in m^2) of the leaf? (b) If, instead, the gold is drawn out into a cylindrical fiber of radius 2.900 mm, what is the length (in m) of the fiber?

    I have already solved part a, but am uncertain how one solves part b? I just need a hint or two to get started on the right direction. Do I just convert the units accordingly or do I need to obtain more information first? I was able to solve part a by simply converting the 9 oz. of gold into cubic centimeters using the information given and then further converting from there, but that doesn't seem to work for part b, unless I did my math wrong somewhere. Please help! Thanks!
  2. jcsd
  3. Jan 15, 2006 #2
    Still stumped... can't anyone help?
  4. Jan 15, 2006 #3
    find the mass of the gold, and change it into volume. now divide this volume by the cross section area of the wire. make sure to use the right units.
  5. Jan 15, 2006 #4
    The formula for a volume of a cylinder is V=pi*r2*L. Since you have already calculated the volume of gold (V), and are given the radius (r), it should be simple to find the length of the fiber (L).
  6. Jan 15, 2006 #5
    Thanks for your help!
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