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Homework Help: Kinematics Question

  1. Sep 30, 2006 #1
    Q: A plane is flying horizontal to the ground with uniform velocity Vo. A stone is thrown at it with velocity V1 and angle alpha to the horizontal. If the stone hit the plane, at what height is it flying?

    The simple equations of uniform acceleration are available to me.

    We obviously have to equate

    x coordinate of plane during collision = x cooridinate of stone during collision
    y coordinate of plane during collision = y coordinate of ston during collision.

    I have attached an image of how I percieve this question. Sorry for the crappy drawing.

    Anyway, my question is how to write the equations of motion for the plane and stone. Thank you.

    Attached Files:

  2. jcsd
  3. Sep 30, 2006 #2


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    Staff Emeritus
    Science Advisor

    Determine the initial vertical velocity of the stone, then relate the height it achieves in terms of initial velocity and constant acceleration (or deceleration) due to gravity.


    The stone has to achieve the same altitude, then it has to be at that altitude at the same time.

    Basically, the problem is one of intersecting curves/trajectories.
  4. Sep 30, 2006 #3
    But it doesnt hit the plane at its maximum height. Or am I missing something?
  5. Sep 30, 2006 #4

    Doc Al

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    Staff: Mentor

    Are we to assume that the stone is thrown at the instant that the plane passes directly overhead? If so, take advantage of that information.
  6. Sep 30, 2006 #5
    you should use the equation S= ut +1/2 at^2
    or in this case S= ut - 1/2 gt^2
    v^2=u^2 + 2as
    I sincerely believe there are some information missing
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