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Homework Help: Finding time of a rocket

  1. Sep 20, 2015 #1
    1. The problem statement, all variables and given/known data
    A model rocket takes off from ground level accelerating upward at a = 3.0 g. This upward acceleration lasts for a time τ = 15 s. Afterward the rocket continues upward, eventually stops rising, then falls back to the ground.
    How much time passes from the initial upward acceleration stopping to the rocket returning to the ground?

    2. Relevant equations
    constant acceleration

    3. The attempt at a solution
    i broke them down to two different moments (1. during the blast off, 2. when it comes back down.)

    moment 1: let t = τ , vf = aτ , ∆y = 1/2 aτ^2

    moment 2 : 1) ∆y = vot + 1/2at^2
    aτ^2 = aτ - 1/2gt^2
  2. jcsd
  3. Sep 20, 2015 #2


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    Staff Emeritus
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    The "attempt at a solution" means, you know, actually working out the solution, not just throwing a few equations out at random.
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