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Homework Help: Mechanics question in 3D

  1. Aug 19, 2009 #1
    1. The problem statement, all variables and given/known data
    A parachutist jumps from a plane which is at position S = [0, 5000, 0] at time t = 0. The starting velocity of parachutist is v = [300, 0, 100] and we're assuming the parachutists falls like a particle with constant acceleration a = [2, -9.81, 0].

    I need to find the parachutists position after 10 seconds.

    2. Relevant equations
    the only equations i have here are the 3 for accelation under constant motion but these assume a one directional system.

    3. The attempt at a solution
    i can't attempt a solution without knowing where i'm starting here with the 3 dimensions so if anyone could give me a hand with what equations i need to use then i should be good to go!
  2. jcsd
  3. Aug 19, 2009 #2


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    If you know what happens in 1-D, you can easily generalize to 3-D. All you need to do is change symbols. The most general expressions for constant acceleration are

    x(t) = xo+voxt + (1/2)axt2
    y(t) = yo+voyt + (1/2)ayt2
    z(t) = zo+vozt + (1/2)azt2

    In 3-D the position of the parachutist at any time t is [x(t), y(t), z(t)].
  4. Aug 19, 2009 #3
    thank you so much, that's perfect.

    just didn't know if we we're dealing with angular velocity or something more complicated here.

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