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Homework Help: Equation(s) of motion.

  1. Sep 15, 2009 #1
    1. The problem statement, all variables and given/known data
    A student throws a ball 60 ft into the air

    a)How long does he have to wait to catch it on the way down? <----Just needing help on this!
    b)What was its initial velocity?<----and this if a) was solved.
    c)What will be its final velocity?

    2. Relevant equations
    x=V(o)T + 1/2(a)T

    x = Final Position
    V(o) = Initial Velocity
    T = Time (assuming final)

    3. The attempt at a solution

    Attempt was not full proof but was the only way "I" could think of but I know its wrong.

    1st Step: 120 ft. = (0 ft/s)T + 1/2(-32 ft/s^(2))T
    2nd Step: 120 ft. = T + (-16ft/s^(2))T ;Zero disappeared. Multiplied 1/2(-16).
    3rd Step: (120 ft.)/ (-16 ft/s^(2)) = 2T ; Dividing 120/-16. Added Both Time(T) together.
    4th Step: (-7.5 s^(2)) / (2)=T
    5th Step: Got -3.75 s^(2) = T

    Optional Step: Square root -3.75 s^(2) = Nevermind.....Thats why I need help. Can someone walk me through this. Thank You
  2. jcsd
  3. Sep 15, 2009 #2


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    Homework Helper

    Check the relevant equation.
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