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How to find Kepler's law from Newton's laws

  1. Mar 27, 2017 #1
    We were asked to do an experiment where we had to prove the equation:
    T2=(4π2m)/Mgr
    Where M is the mass of the mass stack in kg (0.3kg), m is the mass of the rubber bung in kg (0.0226kg), T is the time taken for one rotation in seconds, r is the horizontal radius of rotation in meters, and g is the strength of gravity (9.8Nkg-1).

    And I tried to relate this to Newton's laws in my report by using:
    F=Mgm/r2
    and F=mv2/r

    Which gave me:
    T2=(4π2r3)/Mg

    How do I reach the original formula using newton's laws?
     
  2. jcsd
  3. Mar 27, 2017 #2
    :welcome:
    Make sure you know there is a difference between "g" and "G".
    g is the acceleration of gravity (about 9.8 m/s2)
    G is the Gravitational Constant (6.67 × 10-11 m3/kg⋅s2)
     
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