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Homework Help: Solve it using energy conservation?

  1. Jan 21, 2010 #1

    majormuss

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    Gold Member

    1. The problem statement, all variables and given/known data
    I just came across this question and i think its giving me a real hard time.
    This is part of a bigger question so I'll provide the other statements below
    7 The maximum height reached by the ball is
    approximately
    (1) 1.2 m (3) 4.9 m
    (2) 2.5 m (4) 8.5 m

    2. Relevant equations
    t=1 s and therefore half way is 0.50s
    V(i)=8.9m/s
    angle is 35 degrees
    Viy= 4.9m/s


    3. The attempt at a solution
    First of all, why is it that I can't use certain formulas in Solving some motion problems even though everything seems to work ok. I tried using this formula....d=V(i)t +1/2at^2... but my answer turns out wrong. and this one rather gives me the answer...Vf^2=Vi^2 + 2ad.......why is that?
     
    Last edited by a moderator: Jul 18, 2014
  2. jcsd
  3. Jan 21, 2010 #2
    Re: Kinematics

    Since you know the initial velocity, why not try to solve it using energy conservation?
     
  4. Jan 21, 2010 #3

    tiny-tim

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    Science Advisor
    Homework Helper

    Hi majormuss! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    All the standard constant acceleration formulas will work. :wink:

    I expect you got t = 0.5 s wrong … where did that come from?
     
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