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Homework Help: Physics velocity problem

  1. Sep 28, 2005 #1
    A stream of water is shot with an initial speed of 2.3 m/s at a beetle on a leaf 3cm above the waters surface. If the fish aims in such a way that the stream of water is moving horizontally when it hits the beetle what is the launch angle.

    Because the stream is moving horizontally then Vy = 0 m/s.
    Ay = -9.8 m/s (gravity)
    Displacement y (Dy) = 3 cm
    Initial V = 2.3 m/s

    How can i find the launch angle

    Dy = Initial Vy * Time + 1/2(Ay)* Time*Time but dont know time or Vy

    and i know nothing for x.
  2. jcsd
  3. Sep 28, 2005 #2
    If the stream is moving horizontally, then it is at the peak of its jump. Vy = 0 at h = 3cm. You can use this to find the time.
  4. Sep 28, 2005 #3
    but i am not given Vy i am givin Initial V which is the square root of Vy squared plus Vx squared. And i cannot derive either of those because i dont have an angle to work with.
  5. Sep 29, 2005 #4
    You can find Vy because you know it is such that [itex] v_{y0}t = -\frac{1}{2}gt^2 [/tex], the moment it hits the leaf, all the upward velocity has been lost to gravitational pull.
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