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Projectile Question ,,

  1. May 19, 2009 #1
    1. The problem statement, all variables and given/known data
    Hi everyone ,, yesterday I had an exam with the following question :
    A ball is vertically thrown from a height (h) then it collide with the ground and went to height (5+h), the whole time of the projectile is 2 seconds .

    (a) Find the initial velocity and the time it took until it reached the ground.
    (b) Find (h) and the velocity before hitting the ground

    2. Relevant equations

    3. The attempt at a solution
    The question was really hard ,, I didn't really know how to solve it .. I applied the following :
    t1+t2=2 ,, and t1 (the time until it reached the ground) and t2(the time until it reached the height (h+5) , the equation of t1 (h=Vot1+0.5*g*t1^2) and for t2 (5-h=(V+gt1)t2-0.5*g*t2^2) and I combined them together and got V=7.5 m/s .. is it right ?? .. is the attempt to solve is even right ??

    Attached Files:

  2. jcsd
  3. May 19, 2009 #2


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    Homework Helper

    Can't see the picture.

    Is the ball thrown initially downward? That's what your equations reflect.
  4. May 19, 2009 #3


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    That doesn't look quite right.

    Wouldn't it be more like

    h + 5 = (V0 +g*T1)*T2 - 1/2*g*T22

    Is the 5 - h a typo ?
  5. May 20, 2009 #4
    it's true ,, it's h+5 ,, but can you tell me what is the answer you got ,, I just wanna know if my answer is right or wrong
  6. May 20, 2009 #5


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    Sorry I didn't solve it. It looks a little tedious.
  7. May 20, 2009 #6
    it took me 1:30 hour in the exam and am still not sure if it's right or wrong -_-
  8. May 20, 2009 #7


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    Well, you'll find out soon enough then. It's not like you can change it now.

    Good luck.
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