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Homework Help: Terminal Velocity + Drag Force

  1. Oct 9, 2009 #1
    1. The problem statement, all variables and given/known data

    A sky diver of mass 79.5 kg jumps from a slow-moving aircraft and reaches a terminal speed of 53.0 m/s.

    (a) What is the acceleration of the sky diver when her speed is 30.0 m/s?

    What is the drag force on the diver when her speed is the following?
    (b) 53.0 m/s (answer in N)
    (c) 30.0 m/s (answer in N)

    2. Relevant equations

    3. The attempt at a solution

    I found parts a and b (correct on Webassign), but I can't get part c.):

    a.) a= 6.792 m/s2
    b.) 779.1 N

    Would part c.) just be: mg-ma???

    = 239.096 (WebAssign says it's incorrect)
  2. jcsd
  3. Oct 9, 2009 #2


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    Homework Helper

    Drag force in air ia approximately proportional to v^2. So f = D*v^2.
    Using the result from b, find D.
    Use this value to solve c.
  4. Oct 9, 2009 #3
    Thanks. I got it.
  5. Oct 9, 2009 #4


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Your answer looks good. Does WebAssign concern itself with doing significant figures properly?
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