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Homework Help: Acceleration due to gravity

  1. Nov 14, 2004 #1
    Ok, please tell me if i am correct, or totally out of it :confused:

    What is the acceleration due to gravity on the surface of
    (a) the Moon (R=1.74x10^3km, m= 7.35x10^22kg)
    (b) Mars (R=3.40x10^3km, m= 6.42x10^23kg)

    i used v= square root of m/R

    for a i got 6.4993x 10^9
    for b i got 1.3741 X 10^10

    is this correct, cause i really am not confident :rofl:
     
  2. jcsd
  3. Nov 14, 2004 #2
    k i took a different approach please tell me which one is the correct one:
    this time i took Gm/R^2 to get the acc.

    for a i got 1.62 m/s^2
    o.0 sorry i really have no clue what I am doing :frown:
     
    Last edited: Nov 14, 2004
  4. Nov 14, 2004 #3
    You should use the second one. Basically, they are all originated from [tex]\frac{GMm}{R^2}[/tex]. You got the first one by equalling it to centripedal force and the second to [tex]mg[/tex].
     
  5. Nov 14, 2004 #4
    k so then the second equation is the correct one? TY o:)

    Another question since the R is in km should I change it to meters?
     
    Last edited: Nov 14, 2004
  6. Nov 14, 2004 #5
    Yes, you have to change them to SI unit.
     
  7. Nov 14, 2004 #6

    Janus

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    yes, you should.
     
  8. Nov 16, 2004 #7
    thank you !!
     
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