blue powder
Registered User regular

I've been looking into the physics of gravity and the like, out of both preperation for next sem and curiosity. I'm trying desperately to understand the theory of gravitation, specifically through the "Feynman lectures on physics volume 1,2 and 3". I have a relatively good understanding of Algebra and Calculus, but I'm having difficulty understanding some of the concepts.

Specificically I'm here to ask what this means: "It is that every object in the universe attracts every other object with a force which for any two bodies is**proportional to the mass of each and varies inversely as the square of the distance between them**."

I can't visualize how something acts inversely as a square. Can someone show me mathematically what this means and maybe direct me towards a diagram or something? I've looked it up but I can't manage to get my mind around it, especially in the context of gravitational pull. Thanks in advance!

Also: this is from the chapter "the theory of gravitation" on page 69 of the PDF file.

Specificically I'm here to ask what this means: "It is that every object in the universe attracts every other object with a force which for any two bodies is

I can't visualize how something acts inversely as a square. Can someone show me mathematically what this means and maybe direct me towards a diagram or something? I've looked it up but I can't manage to get my mind around it, especially in the context of gravitational pull. Thanks in advance!

Also: this is from the chapter "the theory of gravitation" on page 69 of the PDF file.

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## Posts

Diagram (forget the labels, just look at the curve):

FunkyWaltDoggong (force) = (G (constant) * M1 * M2 (masses of the objects in question)) / (x^2) (where x is the distance between them)

basically it means that the force of gravity gets weaker quadradically with respect to distance and linearly with respect to the mass of one object.

you can also think of it as

g = G * (M1/x) * (M2/x)

Dunadan019onHalberdBlueon1/(d^2), where d is your distance (inverse because it lowers it as your distance increases. To be directly proportional to a squared distance would be where d^2 is the driver. The rest is a bunch of constants and mass variables.I should read responses before replying.

Zombie NirvanaonDjeetonInverse square works on a variety of waveforms. We don't know if gravity is a waveform, but it does work on inverse square to a good approximation. The basic idea is that there's only so much power (using that term loosely) in the wave, and that the wave expands as it travels.

So the total effect is the same but the area of the wave is going up. And, as you learn late in algebra (or at least I did), the area increases as the square of the distance it has traveled.

So

effect*area = constant = effect*(something*distance^2)

effect = constant/(something*distance^2)

and there's your inverse square law.

ProPatriaMorionOkay, I think I can understand this, and reporduce it mathematically! So if E varies inversely proportional to the square of F, then E = k/F^2?

Thanks a lot, guys!

blue powderonThat is correct, yes.

grungeboxon