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Only given displacement vector and initial speed, solve for theta

  1. Oct 2, 2009 #1
    1. The problem statement, all variables and given/known data
    A ball is thrown with a speed of 70m/s and hits the top of a wall which is 20m tall and 100m away. Find the angle that the ball was thrown at

    2. Relevant equations
    d= V0xt + 1/2 a t^2
    a = Vf-V0/t
    sin^2(theta) = 1 - cos^2 (theta)

    3. The attempt at a solution
    I found the initial velocity in terms of theta V= 70cos(theta) x + 70sin(theta) y
    the part i'm stuck on is apparently we are supposed to find the time from the horizontal displacement somehow. That i am stuck on because it seems like a i have too many variables and not enough information. any help is appriciated
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 2, 2009 #2


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    Homework Helper

    I think you have all the information you need. You can write separate equations for the x and y displacement in terms of theta and t. This is two equations and two unknowns.
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