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Homework Help: Need help calculating maximum height

  1. Jun 6, 2009 #1
    1. The problem statement, all variables and given/known data
    A doctor, preparing to give a patient an injection, squirts a small amount of liquid straight upward from a syringe.
    a) If the liquid emerges with a speed of 1.3 , how long does it take for it to return to the level of the syringe?
    b) What is the maximum height of the liquid above the syringe?

    2. Relevant equations
    i'm really not sure what equation to use

    3. The attempt at a solution
    for part a i use y=(vi)(t)-.5(g)(t^2)

    I'm really not sure about part b, could someone help me with it
  2. jcsd
  3. Jun 6, 2009 #2


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    Homework Helper

    OK. We'll go with 1.3 m/s (you must include units ... it matters).

    The easy way is to observe that

    v = a*t

    so the time to max height will be given by

    1.3 = 9.8*t or t = 1.3/9.8.

    Since total time is time up + time down ... double that giving 1.3*2/9.8

    Since y = 1/2*g*t2 then just use the time found to max height from before of 1.3/9.8
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