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Homework Help: 2D Projectile Motion

  1. Sep 20, 2010 #1
    1. The problem statement, all variables and given/known data
    A person standing on top of a hemispherical rock (a dome rock) of Radius R kicks a ball (initially at rest on top of the rock) to give it horizontal velocity Vx

    A. What must be it's minimum initial speed if the ball is never to hit the rock after it's been kicked?

    B. With this initial speed. ow far from the base of the rock does the ball hit the ground

    2. Relevant equations
    Xf = V0 + VxiT + 1/2AxT
    Vx = VCos(theta)
    Vy = VSin(theta)

    3. The attempt at a solution

    That's the thing I don't even know where to begin. I don't understand what it wants me to find. It gives no variables whatsoever!
  2. jcsd
  3. Sep 20, 2010 #2
    You need to model the dome as a function (i.e a circle with equation x^2 +y^2=r^2 would work). Next you need to derive the position function for the ball. If you set them equal to each other you could solve for the time when the ball hits the rock. Since you want them not to hit, find the minimum value of v0 for which that applies.
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