Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Floating Arm Trebuchet Calculations and Predictions

  1. Feb 1, 2010 #1
    So, like quite a few others on this forum, I am building a trebuchet for a school physics class.
    While I am really enthusiastic about the project (who doesn't love giant medieval war machines?), I may be a little bit over my head in the calculations.

    So I hope I can give enough information, if not, just let me know!

    1. The problem statement, all variables and given/known data
    I have built a F.A.T. (http://www.trebuchet.com/10101 [Broken])
    The oddity with this trebuchet is that it has no arm ratio as the counterweight sits at the very end of the arm, and the arm itself tends to be shorter.

    What I do not understand is:
    1) How can I find the energy with which the projectile is released? Mainly, how do I tell the displacement of the end of the arm (I know how to find Kinetic energy).
    2) How can I implement the sling? By this I mean a few things:
    a) What angle of the sling determines release, and how will that affect angle of release?
    b) How does angle of release from the sling affect its trajectory, or would it just be a simple projectile arc problem solvable with simple kinematics?
    c) How does the sling affect the velocity at release? I am at a dead loss for this one, though I do know that it whips it around, so perhaps a separate energy equation with kinetic energy, caused by the initial speed around a shortened arc? Just not sure how to implement that...

    I believe that covers my questions, and I hope I have provided enough information to get a response.

    Feel free to post back with Calculus, though Kinematics would be easier (though posting both would be best, I had one semester of Calc 1 and didn't do so well, but I understand the basics).

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 5, 2010 #2
    No one?

    I could really use the help.

  4. Nov 19, 2010 #3
    I've scoured the Internet for a mathematical model (or at least an attempt at one) for the behavior of a floating-arm trebuchet and have had zero luck. Is it an intractable problem? I'm tired of culling search hits for kits and plans being peddled by entities that have no concise explanation for FAT principles and operation.

    -Casey Walsh
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook