1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Angle, range and extension in projectile motion?

  1. Jul 11, 2010 #1
    We have a trebuchet which we can adjust the launch angle, and how far the rubber band is pulled back (extension). The rubber band spring constant is constant throughout. I need to find the relationship between the angle of launch and range, and the relationship between the extension and range. This should allow me to finally be given a range, and adjust the angle and extension so as to make the mass land at that spot.

    We are given no equations, but I have been using the kinetic and gravitational potential energy equations.

    I have trial data in which I have calculated the spring constant - at 184 n/m.

    I have calculated an equation which shows EPE = Fx/2 (the area under the trial data graph is EPE, as it is a force (F) vs extension (x) graph).

    On the net I found the equation: u = [tex]\sqrt{Rg/2sin20}[/tex]


    How should I go about solving this? We need to collect data from repeated tests etc, its an investigation.

    Thanks a lot! :)
  2. jcsd
  3. Jul 11, 2010 #2


    User Avatar
    Homework Helper

    The energy in the spring is 1/2kx2 which is converted into KE as the mass leaves the rubber band.

    so you will have by conservation of energy 1/2kx2 = 1/2 mv2 with v being your initial velocity.
  4. Jul 11, 2010 #3

    So I shouldn't get the speed at the top of the ramp, so it would be KE + MGH?

    What else can I do?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook