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Homework Help: Velocity and displacement *sigh* Isimple! but seems comple

  1. Dec 4, 2013 #1
    1. The problem statement, all variables and given/known data
    A stone is thrown vertically up with a velocity of 20ms/s. The maximum height reached by the stone and the total time taken by it to fall on the ground are

    (1) 20m and 2 s. (2) 20m and 4 s. (3) 40m and 2 s. (4) 40m and 4 s.

    2. Relevant equations
    3. The attempt at a solution
    V = s/t
    V = 20/1 (since the time taken for the stone is 2s to go up and then come falling down, I divided it by 2 and I chose the first answer as it seemed to get my favorable answer)
    V = 20m/s.

    But according to the scheme it's the second answer and I really don't understand how it can come, providing that even if they are divided you get the velocity 5m/s.
    Last edited: Dec 4, 2013
  2. jcsd
  3. Dec 4, 2013 #2
    S = So + Vo*t + (1/2)*a*t^2
    V = Vo + a*t

    These are the equations that you need to use where

    So = initial distance from origin
    Vo = initial velocity
    a = acceleration

    Thats all you need to know to solve this question
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