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Homework Help: Linear drag force

  1. Jun 11, 2013 #1
    1. The problem statement, all variables and given/known data
    We sink ball with density 1450 kg/m^3 in some liquid with density 1400 kg/m^3

    a) What's acceleration in moment we drop the ball?
    b) With what constant speed will the ball sink in balace? Assuming that the drag force is linear. Radius of ball is 3mm and viscosity of liquid is 200 Pa s.

    2. Relevant equations


    3. The attempt at a solution
    a... acceleration
    ρb=1450 kg/m^3
    ρl=1400 kg/m^3
    g=9,81 m/s^2

    a) That's easy, using the formula and you get a=0,338 m/s^2
    b) Need help here, no idea how to solve
  2. jcsd
  3. Jun 11, 2013 #2
    Have you learned the equation for calculating the viscous drag force (in creeping flow) on a sphere of diameter, when the sphere is moving with a velocity v relative to the viscous fluid?
  4. Jun 11, 2013 #3
    If you mean in colledge probably yes, but me personaly dont know that equation.
  5. Jun 11, 2013 #4
    Google Stokes Law.
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