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Homework Help: Observing A Moving Ball

  1. Sep 17, 2011 #1
    Sitting in a second-story apartment, a physicist notices a ball moving straight upward just outside his/her window. The ball is visible for 0.25s as it moves a distance of 1.05m from the bottom to the top of the window. a) How long does it take before the ball reappears? b) What is the greatest height of the ball above the top of the window?

    Hey, I don't know how to approach these types of problems. Help?
  2. jcsd
  3. Sep 17, 2011 #2


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    Homework Helper

    What type of motion is it?
    What equations apply to that type of motion?
  4. Sep 17, 2011 #3
    It's one dimensional motion in the y direction. And, I think the equations that apply are:

    d = v(initial)t + (0.5)at^2

    v(final)^2 = v(initial)^2 + 2ad
  5. Sep 18, 2011 #4


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    Staff: Mentor

    Do you know the value of a in these equations?
  6. Sep 18, 2011 #5
    Yeah, a = g.
  7. Sep 18, 2011 #6


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    Homework Helper

    should enable you to find something. Take time zero to be when the ball first appears, and call that initial height zero, too. You should then be able to put in numbers for the ball at the top of the window and then solve for the initial velocity at the bottom of the window.

    Finally, use the same equation again to figure out the answer to the first question.
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