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Homework Help: Minimum and maximum angles

  1. Sep 25, 2010 #1
    1. The problem statement, all variables and given/known data
    a football kicker can give the ball an initial speed of 25m/s. what are the least and greatest elevation angles at which he can kick the ball to score a field goal from a point 50m in font of the goalposts whose horizontal bar is 3.44 m above the ground.


    2. Relevant equations
    d = Vit + 0.5at^2

    3. The attempt at a solution
    Dx=distance in x direction
    Dy=distance in y direction
    and so on for Velocity and Acceleration

    V = 25m/s
    Dy = 3.44m
    Vx = 25cos(theta)m/s
    Vy = 25sin(theta)m/2
    Ay = -9.8m/s^2

    t = (Dx)/(Vx) = 50m/(25cos(theta))s

    Now plug everything into an equation for Dy
    Dy = Vy*t + 0.5Ay*t^2
    3.44 = (25sin(theta))(2/cos(theta)) + 0.5(-9.8)(2/cos(theta))^2

    I cannot get an answer for theta out of this equation..

    The proper answers are 31 degrees and 63 degrees but i dot know how to solve it
     
  2. jcsd
  3. Sep 25, 2010 #2
    nevermind i think i solved it. my calculator had a setting messed up somewhere that i couldnt find and kept giving me errors.

    i reset my calculator and was able to solve it.
     
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