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1 projectile question

  1. Oct 16, 2005 #1
    how do i solve for this i only know how to do it with a degree and an Vi

    the question is

    a football is kicked at 45 degrees and travels 120 m before hitting the ground

    and i need

    time in air
    and max hight

    how do i get vcos45 without a velocity?

  2. jcsd
  3. Oct 16, 2005 #2


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    If you did know Vi and an angle, could you work out how far it travelled ?
    How would you do that ?
  4. Oct 16, 2005 #3
    i dont have Vi

    edit: could you work it out for me like with just equations
    Last edited: Oct 16, 2005
  5. Oct 16, 2005 #4


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    I think the rules here are that you cannot get direct help on a homework problem until you have at least shown some of your own work.
  6. Oct 17, 2005 #5


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    You have to find Vi, yes,
    But, if if you did have a value for Vi, and also had an angle, could you then work out the distance travelled.
    Just use symbols and show us some working.
  7. Oct 17, 2005 #6
    This should help you along a bit:


    So t=(2vsin45)/g


  8. Oct 17, 2005 #7
    I think that constitutes giving him to much help. I think there is a equation that makes it simpilar, I'm looking now.
    Ok, found it. Now, lets hope I remember how to layTex.
    [tex] R = (V^2_0 \cdot 2 \cdot sin \theta) / g [/tex]
    this is the formula you use to find [tex] V_0 [/tex] or as some say, [tex] V_i [/tex]
    Last edited: Oct 17, 2005
  9. Oct 17, 2005 #8
    I kinda remember. I want it to put the multipling dots, but instead it puts dots on top. Hmmm.... Guess I will go find out by looking at other tex.
  10. Oct 17, 2005 #9

    is R the distance ?
  11. Oct 17, 2005 #10
    Yes, it is the distance the object has traveled.
  12. Oct 17, 2005 #11


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    It is the horizontal distance the object has traveled. :)
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