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Homework Help: Projectiles launched at an angle not sure if i posted this already?

  1. Dec 16, 2008 #1
    1. The problem statement, all variables and given/known data

    A diver pushes off horizontally from a cliff 35 m above the water, and they must clear rocks that extend 5 m from the base of the cliff. (a)What minimum pushoff speed is necessary to clear the rocks? (b)How long are they in the air?

    2. Relevant equations

    for (b) t=square root of 35/4.9=2.67 s I understand how to derive the time equation.
    for (b) y=v(y direction)t+1/2at^2 x=v(x direction)t

    3. The attempt at a solution

    I solved time already, and I got 1.85 m/s for the initial velocity in the x direction, but I cant get the correct initial velocity in the y direction. Im not even sure what Im doing wrong but its frustrating.
  2. jcsd
  3. Dec 16, 2008 #2
    thats actually not projectiles launched at an angle its horizontal projectile motion sorry-I was looking at an angled problem also, which I could use help with too.
  4. Dec 16, 2008 #3


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    The initial y velocity is "given" in the problem. It is zero, since he pushes off horizontally.
  5. Dec 16, 2008 #4
    Oh ok, so I dont even have to solve for that. So the answer is really the initial velocity in the x direction? 1.85 m/s?
  6. Dec 16, 2008 #5


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  7. Dec 16, 2008 #6
    Ok thanks!
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