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Homework Help: Bottle rocket lab.

  1. Nov 6, 2008 #1
    Check my work please!

    1. The problem statement, all variables and given/known data
    -mass of rocket 140.25g
    -time 6.91s(up and down) -or- 3.46s (one direction)

    Ideally, the rockets were supposed to go straight up and straight down, and even though this obviously didn't happen, we are assuming it did. It is assumed that the time of powered flight is essentially zero and that all of the water in the rocket was released instantly at lift-off, even though that is slightly unrealistic, to simplify the calculations, thus the only mass that needs to be considered is the mass of the rocket with no water inside. Apparently the launch also took place in an environment that has no wind resistance and ignores the rotation of the earth, and only the downward acceleration of gravity (-9.8 m/s) is taken into consideration.
    Find the velocity, maximum height, and impulse (in Newton-seconds)

    2. Relevant equations
    what I used: h=.5gt2 v=gt Impulse=Ft=mv

    3. The attempt at a solution

    h=.5(9.80m/s2)(3.46s)2 = 58.66m

    v=gt = (9.80m/s^2)(3.46s) = 33.91m/s

    Impulse=Ft=mv= (.14025kg)(33.91m/s)=4.756N-s

    So is all of that correct?


    Sorry if this is in the wrong section too. It's an AP Physics course so it is technically undergrad, but not 100% sure.
  2. jcsd
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