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Homework Help: Hardest AP PHysics lab EVERRRRRR

  1. Nov 10, 2004 #1
    now guys, i need your help. in this lab, i am making a rocket with a 2 litter soda bottle with water inside, and air will be pumped in so that rocket will fly up. i need to determine a set of equations that will describe the THRUST of my rocket as a function of TIME or MASS or both. we can use M*(delta)v=dm*Ve and Vf-Vi=Ve*ln(Mi/Mf) and whatever other equations will help. Thrust= M(dv/dt) or Ve*(dM/dt).
  2. jcsd
  3. Nov 10, 2004 #2
    Start with Newton's second law,

    [tex] F = \frac{d}{dt} mv [/tex]

    and keep in mind that mass is no longer constant, so you must apply the chain rule.

    [tex] F = \frac{d}{dt}\left( mv\right) = v\frac{dm}{dt} + m\frac{dv}{dt} [/tex]

    See what you can do from there.

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