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## 03 October 2011

### What does g mean?

(From a note to my class folder after a lab writeup:)
 From NASA:  Recognize the guy in "zero g"?  (Or *is* he in "zero g"?)

The variable g represents the gravitational field, which near earth is 10 N/kg.

Or, the variable g represents the free-fall acceleration, which on earth is 10 m/s2.

The variable g does NOT represent the "force of gravity" or the "gravitational pull."  The force of gravity on an object is the object's weight, or mg.

The variable g does NOT represent the "free-fall velocity."  Such a thing does not exist.

And finally, the variable g does not mean "gravity."  That's ambiguous -- lost of quantities are associated with this nebulous thing called gravity.  There's gravitational field and free-fall gravitational acceleration, but also gravitational force, gravitational potential energy, and the universal gravitation constant.

GCJ