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Question on Terminal Velocity finding time

  1. Sep 2, 2013 #1
    1. The problem statement, all variables and given/known data
    I have two skydivers umping out of a plane at 5000m . Skydiver A is using extended arms and reaching a terminal velocity of 41.53m/s. Skydiver B jumping 20 second later headdown and reaching a terminal velocity at 90 m/s. The question is to find the time the second diver must dive in the headdown position to reach Skydiver A. I know the drag forces for each of the skydivers. Cofnused on how to find the time. The answer of the time is 37 seconds but not sure how to get there


    2. Relevant equations
    kinematics? vf=vi + at


    3. The attempt at a solution

    im not sure I tried using vf^2=vi^2+ 2as to find distance from the earth
    but the number didnt make sense to me. I think I got 88 m from earth to reach
    terminal velocity... not sure...
     
  2. jcsd
  3. Sep 2, 2013 #2
    im not sure I tried using vf^2=vi^2+ 2as to find distance from the earth
    but the number didnt make sense to me. I think I got 88 m from earth to reach
    terminal velocity... not sure...[/QUOTE]

    This equation only works if you have a constant acceleration, but do you have that in this case? What about after you reach terminal velocity?

    Are you given a time that it takes to reach the terminal velocity?
     
  4. Sep 2, 2013 #3
    This equation only works if you have a constant acceleration, but do you have that in this case? What about after you reach terminal velocity?

    Are you given a time that it takes to reach the terminal velocity?[/QUOTE]

    no it doesnt:( but yes after if your terminal velocity...theres no time in the problem...not sure what to do..
     
  5. Sep 2, 2013 #4
    You are supposed to ignore whatever happens before they reach their terminal velocities, and just use the terminal velocities to solve the problem.
     
  6. Sep 2, 2013 #5
    What do you have for the drag forces?
     
  7. Sep 2, 2013 #6
    how would I go about that?
     
  8. Sep 3, 2013 #7
    Assume that both divers acquire their terminal velocities immediately.
     
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