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Homework Help: Circular motion problem

  1. Nov 15, 2008 #1
    1. The problem statement, all variables and given/known data

    If John was stationary in space at eh same distance fromo the sun as the earth is, a.how much force would teh sun be exeerting on John? b.what would be John's acceleration towards the sun? c.what would be the sun's acceleration toward John??

    2. Relevant equations
    Mass of John= 50kg
    Mass of Sun = 2x1030kg
    Fg=G*Msun Mjohn/r2
    Fs=force of the sun
    Fj=force of john
    as=acceleration of sun
    aj=acceleration of john

    3. The attempt at a solution
    Fs= .2964444444 N

    b. aj=4pi2r/T2
    aj= .0059497487m/s2

    c. Would I use the same equation as b, with the same T? or is it a different T??

    thank you for all helps and comments
  2. jcsd
  3. Nov 16, 2008 #2


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    Homework Helper

    Hi phys1618,

    This is right, but there is a more direct method that will also help you in part c. In part a you found the force; what is the relationship between force and acceleration? You should get the same answer.

    Then for part c, do the same procedure to find the acceleration for the sun (which will of course be much smaller).
  4. Nov 16, 2008 #3
    yea, it did gave me the same answer as b
    so for c. I
    Fs=Msun*a of the sun
    .2964444444 N=2x10^30kg* a
    1.48 x 10^-31 m/s^2=a

    thank you for the help!!!
  5. Nov 16, 2008 #4


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    Homework Helper

    Sure, glad to help!
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