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Need assistance solving for Intial velocitieswith only angle, range and max height

  1. Sep 18, 2012 #1
    1. The problem statement, all variables and given/known data

    A basketball player is standing 9.5 m from the basket, which is at a height of 3.1m. she throws the ball from a initial height of 2m at an angle of 35 degrees above the horizontal. The ball goes through the basket. Determine intial velocity.





    2. Relevant equations

    Vx = Dx/t

    v2^2 = v1^2 + 2ad

    Dy = (V sine∅) - 0.5GT^2


    3. The attempt at a solution

    I took only half the parabola diagram and assumed v2 is 0 m/s

    Vert

    v1 = ?
    v2 = 0 m/s
    a = -9.8 m/s^2
    max height = 1.1 m

    I used the equation

    v2^2 = v1^2 + 2ad

    and got v1 as 4.64 m/s and from there on on I found initial velocity at an angle.

    BUT the textbook gives a different answer (11m/s) as the initial velocity at an angle.

    I can't figure out why I'm getting this wrong and my teacher sasys she will come back to me as she can't figure the mistake in mine... so help LOL

    PS I assumed the max height of the parabola of the ball is 1.1 m otherwise I couldn't think of any other way.

    Am I doing to this problem right? please post your work if any :)
     
  2. jcsd
  3. Sep 19, 2012 #2

    lewando

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    Gold Member

    Re: Need assistance solving for Intial velocitieswith only angle, range and max heigh

    You have already posted this problem and I have given you an approach to follow. Since you have posted slightly more information here, how about we stay with this one to keep this from getting out of control. Your original post:
    https://www.physicsforums.com/showthread.php?t=636913
     
    Last edited: Sep 19, 2012
  4. Sep 19, 2012 #3

    lewando

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    Gold Member

    Re: Need assistance solving for Intial velocitieswith only angle, range and max heigh

    Use:
    Vx = Dx/t
    Dy = (V sine∅) - 0.5GT^2

    You have 2 equations and two unknowns (V and T). Should I just tell you that Vx = V cos∅, or was that already clear in your mind?
     
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