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Help Finding Average Acceleration

  1. Jun 4, 2012 #1
    1. The problem statement, all variables and given/known data
    NASA operates a 2.2 second drop tower at the Glenn Research Center in Ohio, where experimental packages are dropped from the top of the tower.
    a) What is the drop distance of a 2.2 s tower?
    b) How fast are the experiments traveling when they hit the airbags at the bottom of the tower?
    c) If the experimental package comes to rest over a distance of .75 m upon hitting the airbags, what is the average stopping acceleration?


    3. The attempt at a solution
    I'm pretty sure I've got a & b correct, but I'm not sure how to go about solving part c. Can someone help me please?

    a) What is the drop distance of a 2.2 s tower?
    x = 1/2*gt2 = .5*9.81*2.22 = 23.74 m

    b) How fast are the experiments traveling when they hit the airbags at the bottom of the tower?
    v = gt = 9.81 * 2.2 = 21.582 m/s

    c) If the experimental package comes to rest over a distance of .75 m upon hitting the airbags, what is the average stopping acceleration?
    I think one formula for acceleration is Δv/Δt but I'm not sure how to use that in this case...
     
  2. jcsd
  3. Jun 4, 2012 #2
    It's worth trying to commit the suvat equations to memory:
    s = length, u = initial speed, v = final speed .... a and t you can probably guess!

    v = u + at
    s = ut + 0.5 at2
    s = 0.5(u+v)t
    v2 = u2 + 2as
    s = vt - 0.5 at2
     
  4. Jun 4, 2012 #3
    You need to determine the stopping time.
     
  5. Jun 4, 2012 #4
    For question (c) its energy problem. Refer to problem(b)
     
  6. Jun 5, 2012 #5
    The distance, initial and final velocities are known. Does this situation not seem to be simply covered by one of the standard suvat equations?
     
  7. Jun 6, 2012 #6
    Indeed, but the OP seemed to have trouble determining which one.
     
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