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Homework Help: Projectile Motion Ball Hurl Question

  1. Mar 26, 2014 #1
    1. The problem statement, all variables and given/known data

    If you can hurl a ball so that its initial speed is 30m/s, what is the widest river you can throw it across?

    2. Relevant equations
    The range equations,


    3. The attempt at a solution

    I know you have to use components so what I got what Vx=30sintheta and Vy=30costheta

    I don't know what to do next or how to sub it in because there isn't a angle given . Can someone please help me. Thanks
  2. jcsd
  3. Mar 26, 2014 #2


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    Homework Helper

    You have your formula for the range as

    [tex]d = \frac{v_i sin2 \theta}{g}[/tex]

    For you to throw it at the max range, you'd need to throw it such that your angle θ and hence sin2θ is maximum.

    What is the maximum value that sin2θ can be?
  4. Mar 26, 2014 #3
    Forgot a square!
  5. Mar 26, 2014 #4
    The angle must be 45 degrees to get max range right?
  6. Mar 26, 2014 #5
    Oh ok, I got the answer. Thanks so much !!
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