G-force

This article is about the physics concept. For other uses, see G-Force (disambiguation).
"G's" redirects here. For other uses, see GS.

In straight and level flight, lift (L) equals weight (W). In a steady level banked turn of 60°, lift equals double the weight (L = 2W). The pilot experiences 2 g and a doubled weight. The steeper the bank, the greater the g-forces.
This top-fuel dragster can accelerate from zero to 160 kilometres per hour (99 mph) in 0.86 seconds. This is a horizontal acceleration of 5.3 g. Combining this with the vertical g-force in the stationary case using the Pythagorean theorem yields a g-force of 5.4 g.

The g-force or gravitational force equivalent is 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/s2.[1] More transient acceleration, accompanied with significant jerk, is called shock.[citation needed]

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.[2][3]

The g-force experienced by an object is due to the vector sum of all gravitational and non-gravitational forces acting on an object's freedom to move. In practice, as noted, these are surface-contact forces between objects. Such forces cause stresses and strains on objects, since they must be transmitted from an object surface. Because of these strains, large g-forces may be destructive.

For example, a force of 1 g on an object sitting on the Earth's surface is caused by the mechanical force exerted in the upward direction by the ground, keeping the object from going into free fall. The upward contact force from the ground ensures that an object at rest on the Earth's surface is accelerating relative to the free-fall condition. (Free fall is the path that the object would follow when falling freely toward the Earth's center). Stress inside the object is ensured from the fact that the ground contact forces are transmitted only from the point of contact with the ground.

Objects allowed to free-fall in an inertial trajectory, under the influence of gravitation only, feel no g-force – a condition known as weightlessness. Being in free fall in an inertial trajectory is colloquially called "zero-g", which is short for "zero g-force". Zero g-force conditions would occur inside an elevator falling freely toward the Earth's center (in vacuum), or (to good approximation) inside a spacecraft in Earth orbit. These are examples of coordinate acceleration (a change in velocity) without a sensation of weight.

In the absence of gravitational fields, or in directions at right angles to them, proper and coordinate accelerations are the same, and any coordinate acceleration must be produced by a corresponding g-force acceleration. An example of this is a rocket in free space: when the engines produce simple changes in velocity, those changes cause g-forces on the rocket and the passengers.

  1. ^ Deziel, Chris. "How to Convert Newtons to G-Force". sciencing.com. Archived from the original on 29 January 2023. Retrieved 17 January 2021.
  2. ^ G Force Archived 25 January 2012 at the Wayback Machine. Newton.dep.anl.gov. Retrieved on 14 October 2011.
  3. ^ Sircar, Sabyasachi (12 December 2007). Principles of Medical Physiology. Thieme. ISBN 978-1-58890-572-7. Archived from the original on 21 July 2023. Retrieved 21 September 2020.