The g-force of an object is its acceleration relative to free fall. On earth this is 1g, or 9.8 meters per second squared (m/s^2) or equivalently 65 9.806newtons of force per kilogram of mass. Astronauts experience unusually high and low g-forces. G-force can also be seen on rollercoasters. When the coaster goes down the drop, you are pushed back into your seat because of g-force.