1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Density of Gold

  1. Aug 17, 2014 #1
    1. Problem: Gold, which has a density of 19.32 g/cm3, is the most ductile metal and can be pressed into a thin leaf or drawn out into a long fiber. (a) If a sample of gold with a mass of 2.274 g, is pressed into a leaf of 8.678 μm thickness, what is the area (in m2) of the leaf? (b) If, instead, the gold is drawn out into a cylindrical fiber of radius 2.200 μm, what is the length (in m) of the fiber?

    2. Relevant equations: a=pi x r^2 and (a)(l)= part a

    3. The attempt at a solution: part a= 0.01356, and I tried plugging it into the equation (1.521x10^-11 m^2)(l)=0.01356

    If anyone could find the error in part B!! Please Help
  2. jcsd
  3. Aug 17, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Units? Showing your work?
  4. Aug 17, 2014 #3


    User Avatar
    Science Advisor
    Homework Helper

    The "(a)(l)= part a" looks wrong. The answer to part a is an area. You cant say "area times length = area".

    That looks right (except you forgot the units).

    I don't understand what you did for part (b).
  5. Aug 17, 2014 #4


    User Avatar

    Staff: Mentor

    Don't forget that the leaf has two sides, so there are two surface areas. This could be a trick question! :smile:

    So state your answer as ... m2 per side for each of 2 sides.

    If you knew the shape, you could also work out the area of its other very narrow side/s. :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted