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EK Physics Lesson test 3, discrete

Discussion in 'MCAT Discussions' started by aa4, Jul 27, 2006.

  1. aa4

    aa4 Member

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    can someone please explain to me why the answer is b. i would guess it to be d, g decreases to 0, wouldn't the PE have to as well (PE=mgh)

    thanks

    A rocket is launched from earth to explore our solar system and beyond. As the rocket moves out of the earth's atm and into deep space the gravatational constant g decreases and approaches 0, and the gravatational potential E of the rocket:
    a) also decreases and approaches 0
    b) continually increases
    c) remains constant
    d) increases at first and then decreases and approaches 0
     
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  3. moocow012

    moocow012 New Member

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    PE = mgh refers only to the PE within the earth's gravitational pull. This PE is commonly used because many questions refer to objects within a gravitational field. But In general, PE increases with increasing height, so even if you left earth's gravitational pull, PE will continue to increase. Hope that helps.
     
  4. estairella

    estairella Senior Member

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    To add to that, technically, you can never leave earth's gravitational pull, until you are infinitely away from it.

    Like he said, PE = mgh is an approximation. Imagine an isolated universe with 2 balls of some mass. No matter how much you move them away, there will always be the attractive force of gravity. And because there is always a net attractive force, no matter how small, the farther away you separate them, the more potential energy they have.
     
  5. DrBowtie

    DrBowtie Final Countdown
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    The formula is U=-Gmm/r
    As r-> infinity it gets closer to zero aka increases.

    Enjoy!
     
  6. aa4

    aa4 Member

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    thanks for the help. makes more sense now
     
  7. Dart1516

    Dart1516 Junior Member

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    You know EK has a message board right? Just thought I'd put that out there if you don't know. It stores old questions which have already been asked and the editor of the prep books responds to your new questions.
     

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