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Homework Help: Im so lost help

  1. Sep 18, 2009 #1
    1. The problem statement, all variables and given/known data

    A ball is thrown straight up with an initial speed of 40 m/s. (Neglect air resistance.)
    How high does it go? how long does it stay i the air

    2. Relevant equations

    i know the second part is 8 because its basically saying 40m every second divide by acc.(gravity) which is basically 10 and multiply by 2 one second going up and another going down. but im completely lost on the first part

    3. The attempt at a solution

    im not sure but i think i use the formula for displacement? but when i tried the answer was wrong.
  2. jcsd
  3. Sep 18, 2009 #2
    Write the three motion equations here. And then see what you are looking for.
    What is the final velocity?
    What is initial velocity?
    What is distance? - not known
    What is time? - not given
    What is acceleration?

    You should try equation with time in it when finding the distance.
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