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Gravitational field of mars

  1. Dec 19, 2008 #1
    1. The problem statement, all variables and given/known data
    A 250-kg space probe weighs 935 N on the surface of Mars. What is the gravitational field strength on the surface of Mars?


    2. Relevant equations
    W=mg
    g=Gm1/r^2
    Fg=Gm1m2/r^2


    3. The attempt at a solution
    Okay, so at first I thought it would be:
    g=(6.67x10^-11)(6.42x10^23)/(3.38x10^6)^2
    g=3.75 m/s^2

    BUT

    Then I remembered the weight of the probe...What do I do with that?

    Oh wait, brainflash.

    If I went W=mg and changed it to g=W/m
    g=935N/250kg
    =3.74 m/s^2

    ...So which answer is right?
     
  2. jcsd
  3. Dec 19, 2008 #2

    Hootenanny

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    In the first case you have calculated the gravitational acceleration of the probe, that is the acceleration at which a unit mass will experience if it placed a distance r from the probe in the absence of any other fields.

    The latter answer is correct.

    Do you now understand why?
     
  4. Dec 19, 2008 #3
    Yeah, thanks! That helps! :)
     
  5. Dec 20, 2008 #4

    Redbelly98

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    Since both answers were the same, where was the problem?

    I would go with the second solution method, since that is simpler and it makes direct use of the given information about mass and weight.
     
  6. Dec 20, 2008 #5

    Hootenanny

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    How very true. I hadn't noticed that the OP had used the mass of Mars!
     
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