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    • Thread Starter

    thxxx.... got the answer already


    can anyone tell me wht to do for this?

    Q4b OCR Physics A2 pg 87

    the distance between the centres of the Earth and the Moon is 3.8*10^8m. Assume that the moon moves in a circular orbit around the centre of Earth. Estimate the period of this orbit to the nearest day. Note that 1 day = 8.6x10^4s

    at first i thought calculating F from newtons law of gravitation then put it into Centripetal force.... but do I have the velocity of the moon???

    how about kepler's 3rd law???


    F= GMm/r^2
    a = rw^2

    GMm/r^2 = mrw^2
    GM/r^3 = w^2

    should help, it's where keplers law comes from i thnk
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