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Free Fall Problem

  1. Nov 10, 2009 #1
    1. The problem statement, all variables and given/known data
    An object is launched upwards with a velocity of 25 m/s. At what time (or times) will the object be located twenty meters above the ground?


    2. Relevant equations



    3. The attempt at a solution
    I started off with the following variable list:
    Xo=0 Vo=25
    X=0 V=0
    t=? a=-9.8
    Which seems very off to me.
    When trying to solve I got 2.55 seconds. But is there another time where it reaches 20m?
    How do you solve this?
    Thanks!
     
  2. jcsd
  3. Nov 10, 2009 #2

    rock.freak667

    User Avatar
    Homework Helper

    [tex]x=V_0 t-\frac{1}{2}gt^2[/tex]


    will help you. Remember it is going up, reaching maximum height and falling back down to the ground. So at two times it will be 20m up in the air.
     
  4. Nov 13, 2009 #3
    Would my answers be 0.994sec and 1.557sec?
     
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