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Homework Help: Terminal velocity time

  1. Sep 27, 2008 #1
    1. The problem statement, all variables and given/known data
    The terminal velocity of a 2×10−5 kg raindrop is about 7m/s. Assuming a drag force Fd= - bv,
    Assuming a drag force determine the time required for such a drop, starting from rest, to reach 63% of terminal velocity.

    2. Relevant equations
    Fd=-bv
    Sum of F-ma


    3. The attempt at a solution
    I use Fd=-bv to solve for b then used Fd-Fg=ma and reduced that to dv/dt=-g-(bv/m) but don't know how to determine time.
     
    Last edited: Sep 28, 2008
  2. jcsd
  3. Sep 28, 2008 #2

    cristo

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    Staff Emeritus
    Science Advisor

    You need to show some work before we can help you: what have you tried?
     
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