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Homework Help: How does mass come into play in this problem?

  1. Feb 26, 2006 #1
    Where / how does mass come into the following problem?

    A 180 [lb] soldier has an accident: He fell down from a helicopter hovering at 150 [ft] above a snow packed ground. The impact of his body created a 4.1 [meter] crater in the snow. Convert all units into MKS units and find:

    a) His net acceleration in the snow [m/s^2] (assume constant)
    b) the direction of this net acceleration

    If I treat the soldier as just an object in free fall from the time he falls from the helicopter until the time he hits the ground I can find his final velocity just before hitting the ground. Knowing the depth of the crater and the velocity just before hitting the snow and at the bottom of the crater (zero) I thought that I could find his acceleration, but I do not see how mass comes into play here...When he hits the snow m*g will be greater than the normal force but he comes to a stop so the Fn and m*g are equal then...

    Any thoughts / ideas would welcomed.
  2. jcsd
  3. Feb 26, 2006 #2

    Doc Al

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    Staff: Mentor

    Since, as you point out, you have (or can figure out) the initial and final speed, you can find the acceleration. Mass is not needed for that calculation.
  4. Feb 26, 2006 #3
    Thank you for the clarification.
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