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!

Dimensional analysis

  1. Jun 2, 2016 #1
    this question is about dimensional analysis involving a number with units and a number with no units, if the question is already answered in another post please redirect me if not here is a simple example, for example, :

    say i have 2[in]-1. the 1 is dimensionless and the 2 has units of [in]. can I subtract the
    2[in]-1=1[in]?or do i leave it as 2[in]-1.

    this is not from a problem. i was doing dim. analysis on a sol. and ended up with this so i knew i did something wrong, but it got me wondering what to do in a problem that might be stated like this say in a multiple choice.

    thanks for the time.
  2. jcsd
  3. Jun 2, 2016 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Uh, no, you can't just promote pure numbers to dimensions having units on a whim. I'm not sure what 2 in. - 1 (pure number) even means.
    You can add and subtract only like units. Dimensionless numbers have no units, thus they cannot be added or subtracted to any quantities which contain units.
  4. Jun 2, 2016 #3
    ok thanks for taking the time and clarifying.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Dimensional analysis
  1. Spectral Analysis (Replies: 1)

  2. Analysis of structure (Replies: 6)

  3. Comsol Analysis (Replies: 21)

  4. Modal Analysis (Replies: 4)