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How to calculate the efficiency of a trebuchet?

  1. Sep 6, 2012 #1
    1. The problem statement, all variables and given/known data

    Hi, VERY URGENT and im so confused

    Find the efficiency of the optimum trebuchet.

    Optimum trebuchet Specs:
    Counterweight= 5kg
    Sling Length= 78cm (laid out fully)
    Length from fulcrum to load= 44cm
    Length from fulcrum to counterweight=16cm
    Height the weight drops when fired = 29.632cm
    Average range = 23.7733
    Weight of projectile = 46g
    Gravity = -9.8

    2. Relevant equations

    KE= 1/2 mv^2 (no idea what to use this for and when, apparently we needed to, this is why i am so confused. what has it got to do with this?)

    Actual measured range/ (2*(counterweight mass*distance the counterweight falls)/mass of projectile)

    (Force(load)*Distance (load))/( Force(effort)*Distance(effort))

    F=Ma



    3. The attempt at a solution

    23.7733/ (2*(5*0.29632)/0.046)
    = 0.369*100
    = 36.9%

    OR

    (0.046*-9.8*0.44)/(5*-9.8*0.16)
    =0.0253
    =2.53 %

    im so confused
     
  2. jcsd
  3. Sep 6, 2012 #2
    another equation i missed

    GPE= mass of counterweight*gravity* distance weight falls
     
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