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Homework Help: Help on projectile problem

  1. Feb 15, 2010 #1
    1. The problem statement, all variables and given/known data

    a cannon shoots a projectile @ ANGLE OF 60 DEGREES ABOVE HORIZONTAL W INITIAL SPEED OF 30M/S. CALCULATE MAX HT OF PROJECTILE AND ITS RANGE.

    2. Relevant equations
    U^2Sin^2O
    30^2sin^260/9.8 = 67.5m not sure if this is correct!


    3. The attempt at a solution
    U^2Sin^2O
    30^2sin^260/9.8 = 67.5m not sure if this is correct!
     
  2. jcsd
  3. Feb 16, 2010 #2

    tiny-tim

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    Welcome to PF!

    Hi azsx1! Welcome to PF! :smile:

    (have a theta: θ and try using the X2 tag just above the Reply box :wink:)
    Yes (for the maximum height), except you're a factor of 2 out. :wink:
     
  4. Feb 16, 2010 #3
    Thank you! I think im overthinking this, but I tried doing another way with d=v0t + .5at^2 formula. Thought for sure this would work! so i did and got a different answer! ugh. Can you help with range?
     
  5. Feb 16, 2010 #4

    tiny-tim

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    Well, that'd never work, since you don't know d or t. :redface:

    That's why you had to use a formula without t. :smile:
    Yes … but you have to try it first.
     
  6. Feb 16, 2010 #5
    okay, i got t by imputting the initial velocity of the x/y components/ a for gravity. wouldn't this work? Also the range, i just plugged the numbers in formula d=v0t+.5at^2.
     
  7. Feb 16, 2010 #6

    tiny-tim

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    Not following you. :confused:

    Can you put the numbers in?​
     
  8. Feb 16, 2010 #7
    The time it takes the projectile to reach it's peak is calculated by:

    [tex]t = \frac{v_{iy}}{g}[/tex]

    where [itex]v_{iy}[/tex] is the initial vertical velocity (the y-component) and [itex]g[/tex] is the acceleration of gravity (9.8 m/s/s)
     
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