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Is this a typo? Flea Jump

  1. Aug 30, 2008 #1
    1. The problem statement, all variables and given/known data
    I did this problem in my book, then checked the answer, and it showed what must be a typo for answer a (acceleration should be m/s^2 not m/s), and answer c just makes no sense.

    "When jumping, a flea reaches a takeoff speed of 1.0m/s over a distance of 0.50mm."

    a. What is the flea's acceleration during the jump phase?

    b. How long will does the acceleration phase last?

    c. If the flea jumps straight up, how high will it go?

    The book's answer's
    a. 1000m/s
    b. 0.0010s
    c. 5.1cm

    2. Relevant equations


    a= (((vf)^2-(vi)^2) / (xf-xi)) / 2

    a= (((1.0m/s)^2-(om/s)^2) / (5.0e-4m - 0m)) / 2


    (Change in time)= (vf -vi) / a


    Yf= Yi +vi(change in time) + 1/2 (a)(change in time)^2

    3. The attempt at a solution
    a= (((1.0m/s)^2-(om/s)^2) / (5.0e-4m - 0m)) / 2
    = 1000m/s^2

    (Change in time)= (1.0m/s - 0m/s) / 1000m/s^2
    = 0.001s

    Yf=0m +0m/s(0.001s-0s) + 1/2 (1000m/s^2)(0.001s-0s)^2
  2. jcsd
  3. Aug 30, 2008 #2


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    In part c how did you account for gravity?
  4. Aug 30, 2008 #3
    I used the 1000m/s^2 as acceleration instead of gravity, unless the 1000m/s^2 was meant to be used to somehow solve for vi.
  5. Aug 30, 2008 #4


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    I'm sorry but you can't change gravity.

    Your acceleration was just to get to speed over the tiny distance of the fleas' little legs. After that the flea is in the hands of gravity.

    If your initial velocity is 1 m/s how high will it go?

    Any equations that pop to mind?
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