Yes i understand that i posted this earlier, but it was perhaps just glanced over since it had got replies (by me trying to bump it up, sorry, again). But i seriously would like to know how to solve this question ANy help would be appreciated(adsbygoogle = window.adsbygoogle || []).push({});

Note that i have copiedd the question exactly from the test!

Given the sun's mass (Ms = 2 x 10^30 kg) then earth sun distnace (1.5 x 10^11 m) Newtons Constant G = 6.7 x 10^-11 Nm^2 kg^-2 use a GEOCENTRIC reference frame to explain the earth's orbit (approcximate as a circle)

This was a question on my test and at first sight i was shocked.

But geocentric... if geocentric then the earth would be at the centre and the sun would revolve around the sun. Would the sun have its own circular orbit around orbit as well?

So far i have been thinking and thinking (and thinking...) i have no clue. Would the diagram for this look like the one posted here?

this is my effort so farr

the force between the sun an the earth is

[tex] F_{g} = G \frac{m_{sun} m_{earth}}{r^2} [/tex]

the centripetal force of the sun is [tex] F_{C1} = m_{sun} \frac{v_{1}^2}{r_{1}} [/tex]

But since the sun is revolving around some axis it also experiences anotehr centripetal force [tex] F_{C2} = m_{sun} \frac{v_{2}^2}{r_{2}} [/tex]

equate all those toegether when the sun is at the max distance

[tex] G \frac{m_{earth}}{r} + v_{1}^2 + v_{2}^2 = 0 [/tex]

and when the minimum distance is taken

[tex] G \frac{m_{earth}}{r} + v_{1}^2 - v_{2}^2 = 0 [/tex]

thus [tex] v_{2}^2 = -v_{2}^2 [/tex]

thus v2 = 0?? Is this good enough?? Is this valid??

i am really supposed to take the Ptolemean system like i have? Or have i lost the point of the question??

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# Homework Help: Use a GEOCENTRIC reference frame to explain the earth's orbit

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