The g-force or gravitational force equivalent is a mass-specific force (force per unit mass), expressed in units of standard gravity (symbol g or g0, not to be confused with "g", the symbol for grams).It is used for sustained accelerations that cause a perception of weight. For example, an object at rest on Earth's surface is subject to 1 g, equaling the conventional value of gravitational acceleration on Earth, about 9.8 m/s.More transient acceleration, accompanied with significant jerk, is called shock.
When the g-force is produced by the surface of one object being pushed by the surface of another object, the reaction force to this push produces an equal and opposite force for every unit of each object's mass. The types of forces involved are transmitted through objects by interior mechanical stresses. Gravitational acceleration is one cause of an object's acceleration in relation to free fall.