Re: ZetaTalk and Spaceguard UK (D8)

In Article  <[email protected]> Greg Neill wrote:
>>>>  Where
>>>>        M1 = Earth = 5.9763e+24 kg
>>>>        M2 = Moon = 7.3508e+22 kg
>>>>         r = 200,000 miles = 3.844E8
>>>>         G = Gravity Constant of Earth = 6.67E-11
>>>> And where the force of gravity between two objects is
>>>> another Newton law:
>>>>         F = G*M1*M2/r^2
>
>>> and the centrifugal force is...
>>>          F = M2*v^2
>>> solve for equality F1 = F2 (if there is a solution, there must
>>> be a balance between the two formulas or the Moon would
>>> fly out of orbit) and you get...
>>>     G*M1*M2/r^2 = M2*v^2 or...
>>>     G*M1/r = v^2, which solved for v gives
>>>     v = sqrt(GM1 / r), which has been stated before
>
>> How can centrifugal force consider ONLY the mass of the
>> orbiting body? Doesn't the Moon have a greater gravity pull
>> to deal with, per the Inverse Square law?  We just don't put
>> these together!  Can't!  They don't work together as Newton
>> is WRONG!
>
> Gravity is the force pulling inwards, and is
>     F = G*M1*M2/r^2.
> Centrifugal force is the outward force, and is equal to
>     F = M*v^2/r
> as shown above.  Got it? Since the gravitational force and centrifugal
> force on a body in free-fall are equal and opposite, the net weight
> is zero.

Equal and opposite?  If Centrifugal force has to EQUAL the force of
gravity pulling inward, it does NOT in this math.  The force inward
takes into consideration both masses.  The force outward is only dealing
with the mass of the secondary. How can they NOT both consider the same
factors!