How this calculator works
Free fall treats gravity as uniform and ignores aerodynamic forces. Initial velocity can be negative for an upward throw. The time-from-distance mode chooses the later nonnegative crossing of the entered downward displacement. All objects share the same gravitational acceleration in this model regardless of mass. Near Earth, the default is standard gravity, 9.80665 m/s2; measured local gravity can differ.
Formula
h = u t + g t^2/2; v = u+gt; t = (sqrt(u^2+2gh)-u)/g.
Worked example
At g = 10 m/s2, a release from rest falls 20 m in 2 s and reaches 20 m/s downward. Starting at 2 m/s downward for 3 s gives 51 m of displacement and 32 m/s final velocity.
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Frequently asked questions
What sign should an upward throw have?
Use a negative initial velocity because this page defines downward as positive.
Why does mass not appear?
In the no-drag model, gravitational and inertial mass cancel, leaving the same acceleration for every body.
Can I model a parachute?
Use the air-resistance calculator. A parachute changes drag, which this model omits.