Understanding Tidal Forces and Their Proportionalities

AI Thread Summary
Tidal forces are inversely proportional to the cube of the distance due to the nature of gravitational potential, which is proportional to 1/r, leading to a second derivative of 1/r³. This relationship results in tidal forces being significantly weaker than standard gravitational forces, explaining why the Moon, despite its smaller size, exerts a stronger tidal influence on Earth than the much larger Sun. The forces in a local Cartesian system in free-fall demonstrate that radial forces point outward while perpendicular forces point inward, contributing to this inverse cube relationship. For further information, resources such as specific physics texts and online explanations can provide more detailed insights. Understanding these principles is crucial for grasping the dynamics of tidal forces.
mprm86
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Why are tidal forces inversely proportional to the cube of the distance, and not to the square, as normal gravity force?
Where can I find more ifo about this?
Thanks in advance.
 
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mprm86 said:
Why are tidal forces inversely proportional to the cube of the distance, and not to the square, as normal gravity force?
Where can I find more ifo about this?
Thanks in advance.
Who said that? The tidal force within a small region of a local Cartesian system in free-fall has forces which are linear in the force. Those forces along the radial axis point away from the origin while those perpendicular to the radial point towards the origin. It is the origin of the coordinates which varies as the inverse cube. See Eq. (4) in http://www.geocities.com/physics_world/mech/tidal_force_tensor.htm

The gravitational potential is proportional to 1/r so the second derivative is proportional to 1/r3.

Pete
 
See an explanation http://stommel.tamu.edu/~baum/reid/book1/book/node36.html
Since they vary with the cube of the distance, tidal forces are very weak. That is why the small Moon exerts on the Earth a much stronger tidal force than the gigantic Sun. If they were linear, as pmb_phy says, the Sun would prevail.
 
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