1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Creating a Solar Model - Excel Help

  1. Mar 15, 2013 #1
    1. The problem statement, all variables and given/known data

    The problem given is...Calculate mI+1 and lI+1 at point xI+1 using equation (5), the values of the slopes at points xI+1 and xI from equation (4), and the values of mI and lI from the previous step.

    Here is a screenshot of my solar model


    2. Relevant equations


    3. The attempt at a solution

    I need help with columns I and J.

    For column I, I have the equation entered as =SUMPRODUCT(I2+1/2*(G3+G2)*B3-B2)

    For J I have =SUMPRODUCT(J2+1/2*(H3+H2)*B3-B2)

    and for some reason I'm getting negative values when as it goes down it should be getting closer to 1

    Thanks in advance!
  2. jcsd
  3. Mar 15, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You need parentheses around B3-B2.
    (Why do you need to use sumproduct? You're not using entire arrays of numbers to calculatd a single cell, are you?)
  4. Mar 15, 2013 #3
    Thank you so much! I knew it was something obvious that would make me look stupid ;)

    To your question...I'm not really sure. I'm excel illiterate and our professor expects us to use it without ever showing us anything.
  5. Mar 15, 2013 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Try removing the SUMPRODUCT() wrapper. I don't think it's doing anything.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted