Calcing Gravitational Pull On Objects

[ProfessorKukui4Life]

Asking because I can’t seem to find this, assuming we even do this at all.

Do we have formulas, or generic calculations, for measuring the gravitational pull an object will have? Like for instance, how strong would one be for having a gravitational pull over an entire planets water.

And if so, where can I find this?

 

[ProfessorKukui4Life]

Bump

 

[DontTalkDT]

The force of gravity an object will have on another object is given by Newton's law of universal gravitation, if that is your question.

 

[ProfessorKukui4Life]

The force of gravity an object will have on another object is given by Newton's law of universal gravitation, if that is your question.

I think so. So for instance, my example.

How could one calc the gravitational pull of effecting the planets water?

 

[DontTalkDT]

Which unit of measurement do you want for "gravitational pull" and what do you mean by "effecting" exactly?

 

[ProfessorKukui4Life]

Which unit of measurement do you want for "gravitational pull" and what do you mean by "effecting" exactly?

My bad. By effecting I mean pushing and pulling the water. Like the moon does.

 

[ProfessorKukui4Life]

Which unit of measurement do you want for "gravitational pull" and what do you mean by "effecting" exactly?

Also @DontTalkDT

Looking at the formula for Newton’s 3rd Law, how do we find the center of mass?

Might be a dumb question, but that’s something I don’t quite understand.

 

[DontTalkDT]

The center of mass is calculated like this, which for constant density simplifies to this.

As for affecting the water like the moon: Well, first the question is what like the moon means. That is not quite clear to me. Should it mean applying as much force on the water as the moon does? If so, how much force that is would need to be calculated first, which can be done by the law of universal gravitation as mentioned above. If you look for how much force a gravity field, that acts as strongly on the waters of earth as that of the moon does, exerts on the waters of earth that is your answer.

If you want to know how much mass the object in question would need to have (assuming the gravity isn't generated artificially viamagic or something), then one would need to know the distance of the center of mass of object and the center of mass of the waters of earth. Given that one can say that the force of gravity between it and the waters of earth should be equal or greater to that between the moon and the waters of earth, one can then easily solve to how much mass the object has. It's pretty much just setting in the value in Newtons laws again.

If you want AP values on the other hand you will need entirely different math, going either into the Kinetic Energy or Potential Energy direction (or maybe by using how much of the earths rotational energy was converted into tidal energy in the last 620 million years).

 

[ProfessorKukui4Life]

If you want AP values on the other hand you will need entirely different math, going either into the Kinetic Energy or Potential Energy direction (or maybe by using how much of the earths rotational energy was converted into tidal energy in the last 620 million years).

Hmm yeah, I was looking to see how much AP this would generally be. Sorry for not clarifying that before. Do we have any calcs done for the latter that one could use as a reference?

 

[DontTalkDT]

According to this the total wattage of earth's tides is 3000 gigawatts, which is 3e+12 Watt, which would be 8-A.
I think that would be equal to the energy of the water movement caused by the moon's gravity...