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Multivariable DE and Momentum Problem

  1. Dec 6, 2009 #1
    Ok, so I am doing a typical momentum problem with a varying mass (here dm/dt > 0). I am also taking into account air resistance (stoke's law essentially). After some manipulations I basically get:

    6πnRv - mg(1 - p(water)/p(object)) = m (d/dt(v)) + v (d/dt(m))

    I know I need to separate the variables but I am lost on how. Thank you for the assistance!
  2. jcsd
  3. Dec 7, 2009 #2


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    Science Advisor

    With only a single equation in two dependent variables, you can't. Just as you cannot solve a single equation for two unknowns.
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