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Homework Help: Calculating viscosity

  1. Sep 10, 2007 #1
    1. The problem statement, all variables and given/known data

    A shearing force of 100 dynes is applied to the side of a rectangular plate of 5 x 10 cm dimensions placed on top of a 0.5 mm high column of Newtonian fluid that is initially at rest. As a result of the shearing force, the plate moves at a speed of 11.2 cm/sec. What is the viscosity of this Newtonian fluid? (5 pts)
    PS: Can you guess what this fluid is?

    2. Relevant equations

    Viscosity = (Force/Area)/(Velocity/Length)

    3. The attempt at a solution

    Force = 100 dynes
    Area= 50 cm^2
    Velocity= 11.2 cm/sec
    Length= .05 cm

    Viscosity = (100/50)/(11.2/.05)
    =.00893 Poise
    =.0000983 CeniPoise

    Can someone double check my work and see if Im on the right track? Im positive I have the right inputs and the right equation, but I have a feeling Im messing up on the units because the answer seems way too low. Thanks in advance!
  2. jcsd
  3. Sep 10, 2007 #2
    I think you moved your decimal place the wrong way when you converted to cP.
  4. Sep 10, 2007 #3
    Yes, yes I did. So then the viscosity would be .893, so would that make the Newtonian fluid be water? Water is at 1 Centipose and thats the closest thing to my answer. Thanks for the look out Nick :smile:
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