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Projectile Flight (LAunch)

  1. May 22, 2007 #1
    1. The problem statement, all variables and given/known data
    Vi= 26.06 m/s
    Mass= 0.5 Kg
    Angle of launch= 45 degrees
    time of flight= 3.61 sec
    range= 64m

    I need to find the force given to the projectile on the cannon during the launch, and due to the formula F=MA, I am missing A, but I have not formula to find the acceleration of launch.


    2. Relevant equations
    Which formula can be used to find the acceleartion of launch, and how to use it, for example calculate it with Vel in y or in x,

    3. The attempt at a solution
    I have tried using
    Vf=Vi + AT
    Vf2=Vo2 + 2ax
    X=Vit + ½at^2

    but each one throws different results, im not sure which one is the right to use,
    any help will b appreaciated.
     
  2. jcsd
  3. May 22, 2007 #2

    G01

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    The projectile accelerates from 0 to 26.06m/s inside the barrel of the cannon. Do you have the barrel length? If you know the length of the cannon barrel you could use one of the formulas you gave to find a.
     
  4. May 22, 2007 #3
    yes the distance it displaces inside the cannon is of .47 meters
     
  5. May 22, 2007 #4

    G01

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    Ok, you should be able to use one of the formulas you listed to find A. Now, which one involves the information you know and the variable your looking for?
     
  6. May 22, 2007 #5
    I guess that this one
    Vf2=Vo2 + 2ax
    Vi is0
    25.06^2=a
    2 x .47

    which gives me like 670m/s2 which is not accurate i think
     
  7. May 22, 2007 #6

    G01

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    That is what I get as well. It looks right for the numbers you supplied.
     
  8. May 22, 2007 #7
    or maybe with the info i have i can find KE= 157 J
    then W=FX
    157/.47= F
    will that b accuratE?
    which is the same which i got with the previous information, thank you
    but the question, do those number look possible??? it was a projectile launched with ethanol...
     
  9. May 22, 2007 #8

    G01

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    Yes, you could do it either way and should get the same answer if you calculated both correctly.
     
  10. May 22, 2007 #9
    Yep im calculateing them right, but hte question if that is those numbers actually look possible for a real life thing?
     
  11. May 22, 2007 #10

    G01

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    157 J of Kinetic Energy seems plausible. What value do you get for the force?
     
  12. May 22, 2007 #11
    334 Newtons,
     
  13. May 22, 2007 #12

    G01

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    It seems reasonable.
     
  14. May 22, 2007 #13
    thank you very much for ur help,
    if by eany reason u know how can i calculate the enregy realsed by the combustion of ethanol.. i would appraeciated it :P
     
  15. May 22, 2007 #14

    G01

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    No problem.




    Sorry, can't help you here, but I'm sure the answer can be found tabulated somewhere.
     
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