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Homework Help: Fluid Mechanics Question: Calculation of kinematic velocity

  1. Aug 23, 2009 #1
    hey guys im new to the forum... i am a first year civil engineering student trying to do a second year course over this summer holiday. for fluid mechanics i was given this h/w problem. could you please tell me if im correct and if not make explain where i went wrong and how to correct it?

    1. The problem statement, all variables and given/known data
    at 25 C a fluid has an absolute viscosity of 0.0978 Poise and a Specific Gravity of 0.997. Compute:
    a. absolute viscosity in Ns/m^2
    b. Kinematic viscosity in SI units

    2. Relevant equations

    Specific Gravity(SG)= Density of substance(Ds)/ Density of Water(Dw)

    Kinematic Viscosity (KV) = Absolute Viscosity in SI units/ Density of Substance(Ds)

    1 Poise= 0.1 Ns/m^2

    3. The attempt at a solution

    1 Poise= 0.1 Ns/m^2


    o.00978 Poise = 0.1 x 0.00978 Ns/m^2 = 0.000978 Ns/m^2


    KV= Abs. Viscosity/ Ds

    SG= Ds/Dw

    Ds= SG x Dw = 1000 kg/m^3 x 0.997 = 997kg/m^3

    KV = (0.000978 Ns/m^2)/ (997 kg/m3)

    => KV= 9.8 x 10^-7 Nsm/Kg
  2. jcsd
  3. Aug 23, 2009 #2


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    Gold Member

    Yes your work is correct.
  4. Aug 31, 2009 #3
    the lecturer showed us a pretty neat way to handle these units...

    Nsm/Kg ->

    since N= Kg/m^2

    units = m^2/ S

    very late dont have time to rbeak down
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