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Homework Help: Calculate gravitational field strength above surface of Mars

  1. May 27, 2015 #1
    1. Calculate the gravitational field strength at 500km above Mars' surface.
    Mass of Mars: 6.39 x 1023 kg
    Radius of Mars: 3.39 x 103 km
    Constant G: 6.67 x 10-11

    2. I used the equation g = GM / r2

    3. To begin with I added the 500km height above ground to the radius, giving 3.89 x 103 km. I then converted this to metres, which is 3.89 x 106 m.

    So subbing this into the formula:
    (6.67 x 10-11) x (6.39 x 1023) / (3.89 x 106)2

    = 2.82 N/kg

    Is this correct? Thanks in advance!
  2. jcsd
  3. May 27, 2015 #2


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    Staff: Mentor

    Looks fine!
  4. May 28, 2015 #3
    Thank you! :biggrin:
  5. May 28, 2015 #4


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    Homework Helper

    I get 3.71 m/s2 ?
  6. May 28, 2015 #5
    @andrevdh , did you use the same formula / figures as I did in the OP?

    I'm very worried about doing this wrong as I have an exam tomorrow.
  7. May 28, 2015 #6


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    This figure is OK, if you are at the surface of Mars. However, the OP asks for the value of gravitational acceleration 500 km above the surface of Mars.
  8. May 28, 2015 #7
    Ah! Thanks so much for clarifying, I was too stressed to spot what he'd done. :-p
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