Gravitational Constant (universal)

[robertroman10]

I was looking at the gravitation constant and I didnt understand the parts of it with kg, and seconds. Could someone please explain in detail how to use this constant and give an example of some calculations?

Thanks

 

[Vagn]

Assuming you don't want General Relativity, then G comes from the Newtonian Law of Universal Gravitation, which is

F=GmM/r^2

Where F is the gravitational force, m is the mass of one object, M is the mass of the other usually larger object, and r is the distance between the centre of masses of the two objects.

We know F has units of Newtons, which can be written as kg m/s^2
We know the units of m, M and r, so we can write G's units as N m^2/kg^2 by rearranging the above equation for G.

 

[robertroman10]

Assuming you don't want General Relativity, then G comes from the Newtonian Law of Universal Gravitation, which is

F=GmM/r^2

Where F is the gravitational force, m is the mass of one object, M is the mass of the other usually larger object, and r is the distance between the centre of masses of the two objects.

We know F has units of Newtons, which can be written as kg m/s^2
We know the units of m, M and r, so we can write G's units as N m^2/kg^2 by rearranging the above equation for G.

so in the rearranged version would the kg be the kiliagrams of the second object and would the first m be the number of kg of the first object? so would it be N=m^2/kg^2?

 

[HallsofIvy]

It's had to understand what you are asking. The "m" and "M" are the masses of the two objects. It doesn't matter which you call the "first object" and which the second. Where VAgn writes "N m^2/Kg^2" is neither the "m" nor the "M" in the original equation- it stands for "meters". And I hope that "=" in "N= m^2/kg^2" was a typo. What he wrote was "N m^3/kg^2. That is, that the units of G are "Newton-meters squared per kilogram squared".

 

[robertroman10]

It's had to understand what you are asking. The "m" and "M" are the masses of the two objects. It doesn't matter which you call the "first object" and which the second. Where VAgn writes "N m^2/Kg^2" is neither the "m" nor the "M" in the original equation- it stands for "meters". And I hope that "=" in "N= m^2/kg^2" was a typo. What he wrote was "N m^3/kg^2. That is, that the units of G are "Newton-meters squared per kilogram squared".

dude...im thirteen I have no idea what the **** you just said