Free-fall

Free-fall or free fall in the strict sense is the condition of acceleration which is due only to gravity. In other words, the objects undergoing freefall experience only one force: their own weight.

Related Topics:
Gravity - Force - Weight

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Examples include:

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• a spacecraft with the rockets off
• the Moon's trajectory around the Earth, or the Earth's orbit around the Sun.

as opposed to the cases where other forces are acting, including:

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• standing on the ground, sitting in a chair on the ground, etc. (gravity is cancelled by the reaction force of the ground)
• flying in a plane (gravity is cancelled by the lift the wings provide) - see below for special trajectories which form an exception
• atmospheric reentry, landing on a parachute: gravity is opposed by atmospheric drag
• during an orbital maneuver in a spacecraft: the rocket provides thrust

More generally, freefall is the condition of acceleration which is due only to gravity and air friction: in parachuting, freefall (skydiving) refers to the act of falling and delaying the opening of a parachute. Freeflying is skydiving in other body positions than the more standard belly flying.

Related Topics:
Parachuting - Parachute - Freeflying

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With air friction acting upon an object that has been dropped the object will eventually reach terminal velocity (around 120 miles/hour for a human body flying in the belly-down arched position; terminal velocity depends on many factors including mass, drag coefficient, and relative surface area) if the fall is from sufficient altitude (2,000 ft) and also otherwise uninterrupted.

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Free-fall: People surviving free fall ►