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Calculating work done by helicopter/gravity, kinetic energy and speed?

  1. Feb 23, 2013 #1
    A helicopter lifts a 90 kg astronaut 13 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/12. How much work is done on the astronaut by (a) the force from the helicopter and (b) the gravitational force on her? Just before she reaches the helicopter, what are her (c) kinetic energy and (d) speed?


    F=ma
    W=Fd
    KE=1/2mv2


    F=ma
    F=(90)(9.8/12)=73.5
    W=(73.5)(13)=955.5

    Was not the right answer for a...for b I tried using Wg=-mgd but that didn't seem to work either. Am I misinterpreting what g/12 means? a and b were as far as I got. :( Any help would be appreciated, thank you!
     
  2. jcsd
  3. Feb 23, 2013 #2

    rude man

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    Gold Member

    Re: Calculating work done by helicopter/gravity, kinetic energy and sp

    There are two forces acting on her. Consider - if the astronaut were just dangling there without moving, is the force exerted by the rope = ma = 0?
     
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