Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Confusing indices question

  1. Nov 14, 2007 #1
    The Volume and surface area of a sphere is 4/3πr^3 and 4πr^2 respectively. V=4/3πr^3 and S=4πr^2. Write a) S in terms of V and b) V in terms of S

    Im stuck on this question... I write out similar base units and stuff but it doesn't seem to work, any help?

    -The answer to part a is S=2^2/3 3^2/3 π^1/3 V^2/3
     
  2. jcsd
  3. Nov 14, 2007 #2
    Apparently what you have to is solve each formula for r, and then plug into the the other.

    So to solve part a) first, solve your Volume formula for r. then plug that into r in your S formula.

    Just do the opposite to solve part b.
     
  4. Nov 14, 2007 #3

    symbolipoint

    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    At least use grouping symbols properly if you do not have mathematical typesetting formatting. You intend to say
    [tex] \[
    V = \left( {\frac{4}{3}} \right)\pi r^3 \quad S = 4\pi r^2
    \]
    [/tex]

    You should see through inspection that S is actually contained in the formula for V.
    [tex] \[
    V = \left( {\frac{1}{3}} \right)(4\pi r^2 )r = \frac{{Sr}}{3}
    \]
    [/tex]
    Right now, I do not yet see a way to completely eliminate 'r' from the formula. ...Should be possible though.
     
  5. Nov 14, 2007 #4

    symbolipoint

    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    David18 has the right method. It will look a little messy but it will work. No need to bluntly show variable r.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Confusing indices question
Loading...