Free fall

Free fall is motion caused solely by gravity, with no other forces acting on an object. Near Earth’s surface, it gives all objects the same acceleration when air resistance is negligible.

Gravitational acceleration: The acceleration produced by gravitational force on an object. It sets the changing velocity of an object in free fall.
Position: The location of an object relative to a chosen reference frame. Free-fall motion describes how this location changes over time.
Drop tower: A tall facility that creates brief microgravity conditions by allowing a capsule to fall freely. Its falling capsule approximates free fall for experiments.
Projectile motion: Two-dimensional motion under gravity after an object is launched, often with air resistance neglected. It combines free fall vertically with constant horizontal motion.
Newton's law of universal gravitation: A law describing gravitational attraction between masses in terms of their masses and separation. It explains the force that produces free-fall motion.
Velocity: The rate and direction of change of an object's position. Gravity changes the velocity throughout a free-fall trajectory.
Parabolic flight: Aircraft flight along a parabolic path that produces brief periods of apparent weightlessness. The aircraft and its occupants share near-free-fall motion along the arc.
Weightlessness: A condition in which an object experiences no supporting contact force and has no felt weight. Free-falling occupants feel weightless even while gravity acts on them.
Equivalence principle: The principle that inertial and gravitational mass are equivalent, making gravity's local effects resemble acceleration. It accounts for the shared free-fall acceleration of different objects.
Acceleration: The rate of change of velocity with time. Free fall is characterized by acceleration due to gravity alone.

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