1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Problem 8.77 A Flea's Jump

  1. Aug 5, 2008 #1
    The resilin in the upper leg (coxa) of a flea has a force constant of about 26 N/m, and when the flea cocks its jumping legs, the resilin in each leg is stretched by approximately 0.10mm .

    Given that the flea has a mass of 0.55mg , and that two legs are used in a jump, estimate the maximum height a flea can attain by using the energy stored in the resilin. (Assume the resilin to be an ideal spring.)


    Thanks for the help!
  2. jcsd
  3. Aug 5, 2008 #2
    You need to make an attempt at a solution, it is not our job to do your homework for you. If you can show effort, than we can be of further assistance, if you are struggling.
  4. Aug 5, 2008 #3
    So you don't know the answer? I have plenty of work on my paper, but it's all chicken scratch.
  5. Aug 5, 2008 #4
    I could work out the answer, but the stickies for this forum give a clear structure for posting, which includes an attempt at the solution. What have you tried so far? What is going wrong?

  6. Aug 5, 2008 #5
    I'm trying to use hooke's law for the spring in the flea's legs.

    which would be F=kx
    F=(26N/m)(2x(for each leg)(0.0001m)
    I got a force of 0.0052

    I thought of using PE=mgh, the only equation I know of that would give me the height.
    I'm sure it's a simple problem I just don't know which equation to plug the given values into.


    1.16x10^-6 = 5.5x10^-6 (9.8)h
    h=2.15cm, but it's wrong.
  7. Aug 5, 2008 #6

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: How much energy is stored in the flea's cocked legs?
  8. Aug 5, 2008 #7
    You're on the right track.

    You have F = kx. Work is force over a distance right? So if you find the integral of F = kx over the interval [0,.10], you can find the enegry stored in the flea's coked legs as Doc Al stated above.

    F = kx => W = 1/2kx^2
  9. Aug 5, 2008 #8
    1/2kx^2 = 1/2mv^2

    then plug into 1/2mv^2=mgh

    h= v^2/2g
  10. Aug 5, 2008 #9

    Doc Al

    User Avatar

    Staff: Mentor

    OK, but you can go directly from spring potential energy to gravitational potential energy. (No need to worry about kinetic energy.)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Problem 8.77 A Flea's Jump
  1. How far can flea jump? (Replies: 2)