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Homework Help: Question about terminal speed using drag

  1. Jul 5, 2010 #1
    What is the terminal speed of a 75 kg man that jumps out of a plane feet first? The man can be thought of as a rectangular box with dimensions 20 cm * 40 cm * 1.8 m

    I tried equation v terminal = sq rt (4mg/p* area). P=1.22
    I used . 72 as Area. That's wrong. Help please!

    I calculated eq using .72 but that is wrong. Help!
     
  2. jcsd
  3. Jul 5, 2010 #2

    ehild

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    What area should be used in the equation for terminal velocity?

    ehild
     
  4. Jul 5, 2010 #3
    See my book says to use the cross sectional area. The answer is supposed to be 170 m/s but I am very frustrated because I can't see how they got that. His cross sectional area is 1.8 m * .40m =.72 but it's wrong if you use this.
     
  5. Jul 5, 2010 #4
    Oh i see what you are saying, since he jumps out feet first, that means the area is .20 * .40, this side meets air resistance. If you use this in the eq the value is 170 m/s and that's the answer. Is my reasoning correct?
     
  6. Jul 5, 2010 #5

    ehild

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    Yes, that is the clue, feet first!!! Good job!

    ehild
     
  7. Jul 5, 2010 #6
    Thanks for all your help!
     
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