G-force
The "g" in g-force stands for gravity
The g-force on something is its acceleration relative to free-fall
G-force
The g-force acting on a stationary object resting on the Earth's surface is 1 g
G-force in weightless environment such as free-fall in a vacuum is 0 g
Pilots in F-15s or similar aircraft would have to endure 9gs for maybe ten to twenty seconds…