Editing Free fall (section)

{{Short description|Motion of a body subject only to gravity}}
{{Other uses|Free fall (disambiguation)}}

In [[classical mechanics]], '''free fall''' is any motion of a [[physical object|body]] where [[gravity]] is the only [[force]] acting upon it.
A freely falling object may not necessarily be falling down in the [[vertical direction]]. If the common definition of the word "fall" is used, an object moving upwards is not considered to be falling, but using scientific definitions, if it is subject to only the force of gravity, it is said to be in free fall.  The [[Moon]] is thus in free fall around the [[Earth]], though its [[orbital speed]] keeps it in [[orbit of the Moon|very far orbit]] from the [[Earth's surface]].

In a roughly uniform [[gravitational field]] gravity acts on each part of a body approximately equally.  When there are no other forces, such as the [[normal force]] exerted between a body (e.g. an [[astronaut]] in orbit) and its surrounding objects, it will result in the sensation of [[weightlessness]], a condition that also occurs when the gravitational field is weak (such as when far away from any source of gravity).

The term "free fall" is often used more loosely than in the strict sense defined above. Thus, falling through an [[atmosphere]] without a deployed [[parachute]], or lifting device, is also often referred to as ''free fall''. The [[aerodynamic]] drag forces in such situations prevent them from producing full weightlessness, and thus a skydiver's "free fall" after reaching [[terminal velocity]] produces the sensation of the body's weight being supported on a cushion of air.

In the context of [[general relativity]], where gravitation is reduced to a [[General relativity|space-time curvature]], a body in free fall has no force acting on it.