“G-force” is the feeling of your speed increasing or changing. When you “put your foot down” i.e. accelerate in a car you feel a g-force due to the car moving faster and your own body reacting by being “pushed” back into your seat.
It’s called “g” force because you have the same sensation all the time being pulled to the ground by *g*ravity. The two sensations are technically indistinguishable if you get into the physics of it.
Latest Answers