# Proportionality Constants

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1. Apr 25, 2015

### Syed Ammar

I wanted to ask how are the values of proportionality constants in physical relations determined. How do we come to know their exact values ???? An explanation with an example please...

2. Apr 25, 2015

### SteamKing

Staff Emeritus
Which proportionality constants do you have in mind?

If you are talking about something like G (the universal gravitational constant), its value is determined through careful experiments. The value obtained is not exact (how could it be?), and there is usually a precision associated with each constant, since different experimental methods have different levels of precision associated with them. For instance, G is the one physical constant which is least precisely known.

http://en.wikipedia.org/wiki/Gravitational_constant

3. Apr 25, 2015

### Syed Ammar

Can you elaborate on constants of other fundamental forces like k in Coulomb's law?

4. Apr 25, 2015

### rumborak

While in the beginning, when Charles-Augustin de Coulomb postulated the law named after him, "k" had an empirically derived value, it now has a precise value, because you can calculate it from other constants. The Wikipedia article on the constant lays out the derivation quite nicely.