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!

Confused about the units of density

  1. Apr 13, 2010 #1
    1. The problem statement, all variables and given/known data
    I'm dealing with densities of liquids.

    When using the formula P = Patm + ϱgh, where ϱ is the density of the liquid, what should the units of ϱ be?

    2. Relevant equations

    3. The attempt at a solution
    I have P in kPa, so just looking at the units gives:
    kPa = kPa + (?)(m/s2)(m) --> kPa = (?)(m2/s2)

    Which would mean the units of ϱ are (kPa)(s2 / m2).

    Somehow that seems wrong... I thought ϱ was supposed to have units of mass per volume?
  2. jcsd
  3. Apr 13, 2010 #2


    User Avatar
    Homework Helper

    1 Pa = 1 N m-2
    1 kPa = 1000 Pa
    1 atm = 101.325 kPa

    1 N=1kg m s-2

    So 1 atm = 101325kg m-1s-2 in the basic Si units.

  4. Apr 13, 2010 #3


    User Avatar
    Homework Helper

    kPa has the same unit as Pa, which can be written as N/m2
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook