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Homework Help: What equation should I use?

  1. Sep 15, 2007 #1
    Ok, for our lab on projectile (2-d) motion,

    We know :

    Angle of launcher(little canon) with respect to surface
    height of launcher abover surface
    average horizontal distance ball traveled at that angle/height
    -9.8 gravity force

    and are required to find the launch speed. What equation should I use to accomplish that?

    Thank you.
    Last edited: Sep 15, 2007
  2. jcsd
  3. Sep 15, 2007 #2
    The equation of motion.
  4. Sep 15, 2007 #3
    which is...?
  5. Sep 16, 2007 #4
    The equation of motion for constant acceleration a:
    [tex] \vec x (t) = \vec x (0) + \vec v(0) t + \frac{1}{2} \vec a t^2 [/tex]
  6. Sep 16, 2007 #5


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    What equation is ALWAYS the basic equation of motion in classical mechanics?
    What is that law called?
  7. Sep 16, 2007 #6
    I don't think I have learned that yet. Don't have a known time in our measurements so that equation wouldn't work. Am I supposed to use the trajectory equation? But would it would it work in this case since the launcher was launching the projectile from a table onto the floor?
  8. Sep 16, 2007 #7
    I hadn't told you to use it if it wasn't an equation that helps you solve your problem. Just count the degrees of freedom: How many real-valued parameters are unknown? How many real-valued equations did I give you?
  9. Sep 16, 2007 #8
    yeah, those riddles are helping a lot.
    Can anyone comment or suggest an equation?
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