How Can One Calculate the Gravitational Constant G by Combining Two Formulas?

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SUMMARY

This discussion focuses on calculating the gravitational constant G by combining two fundamental physics formulas: Fg = G x (m1 x m2 / r^2) and Fz = m1 x g. The participants clarify that G can be expressed as G = (g x R^2) / m2, where g is the acceleration due to gravity (9.81 m/s²), m1 is the mass of the object, m2 is the mass of the Earth, and R is the Earth's radius. The confusion arises when trying to apply these formulas while standing still on Earth, as the distance traveled (s) is zero, leading to undefined results when calculating G. The key takeaway is that G can only be accurately calculated when an object is in free fall, not when stationary.

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  • Familiarity with gravitational formulas and constants
  • Knowledge of basic physics concepts such as acceleration and force
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  • Study the derivation of gravitational formulas in classical mechanics
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  • #31
it is not about measuring g
 
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  • #32
The first words of the thread are about calculating G with a formula containing g. How can you calculate it from g if you don't measure g at some stage? (I now see this has been mentioned at least once before).

Calculating G from g (and other things) is surely just a rearrangement of some formulae. Most of the arguments here seem to involve pulling yourself up by your own bootstraps. You can't do anything without measuring some mass, some forces, some times and some distances, in one form or another. You takes your pick as to which ones and how.
 
  • #33
Siebevp said:
to calculate g you ofcourse need the equation g=GM/r^2,

but every time on one side of the equation there is just one variable of time.
I don't know where you are getting that idea. The only variables are g, G, M, and r. There is no variable of time which would usually be denoted by the variable t.

The rest of your post seems to confuse a dimensional analysis of an equation with the variables of the equation.
 

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