Gravitational acceleration from moon

AI Thread Summary
To calculate the gravitational acceleration on Earth due to the moon, the correct approach involves using the formula a = GMearth/R² - GMmoon/D², where Mearth is the mass of the Earth, Mmoon is the mass of the moon, R is the Earth's radius, and D is the distance from the moon to the object. The previously mentioned formula for tidal influence, a = GMm/(R-r)² - GMm/R², is not directly applicable for calculating gravitational acceleration at a specific point on Earth. The mass of the object being influenced is irrelevant in this context. The discussion highlights the need for clarity in differentiating between gravitational effects and tidal forces. Understanding these distinctions is crucial for accurate calculations.
Irishwolf
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Hi ,
How could I calculate the acceleration of an object on the Earth's surface , say at the equator , from the influence of the moon , when the moon is directly overhead?

I have calculated the force of attraction from the moon to be 1.99 x 10^(20) N.

Now to find the gravitaional acceleration do I use ==> a=F/M
Where big M = mass earth?
I do I use the mass (m) of the moon?
Or is this not the way to calculate it?
-------------------------------------------------------
Another attempt of solving this was i used the formula for influence of moon on tides:
a= GMm/(R-r)^(2) - GMm/(R^(2))
and grav acc due to moon is 0.000001131 m/s^(2)
But someone said I should solve it with the above equation?

Help please
 
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Irishwolf said:
Hi ,
How could I calculate the acceleration of an object on the Earth's surface , say at the equator , from the influence of the moon , when the moon is directly overhead?

I have calculated the force of attraction from the moon to be 1.99 x 10^(20) N.

Now to find the gravitaional acceleration do I use ==> a=F/M
Where big M = mass earth?
I do I use the mass (m) of the moon?
Or is this not the way to calculate it?
-------------------------------------------------------
Another attempt of solving this was i used the formula for influence of moon on tides:
a= GMm/(R-r)^(2) - GMm/(R^(2))
and grav acc due to moon is 0.000001131 m/s^(2)
But someone said I should solve it with the above equation?

Help please

I'm not sure I understand your question. If your question is what is the net acceleration of an object on Earth considering the gravitational effect of the moon, you may look at it with this formula:

a = GMearth/R2 - GMmoon/D2

Mearth = mass of earth
Mmoon = mass of moon
R = Earth radius
D = distance from center of moon to the object.
 
Hi yes that was my question thanks,
But why is that a different formula than the one used to calculate the moons influence on tides?
 
Not sure about tide formula. What does that do?
Note, mass of the object is irrelevant. For tide, is there a
well defined mass? You can treat all ocean water as one massive object,
but then acceleration of what water? Our simple formula then may not be
very accurate.
 

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