Enter a drop height to find the fall time and impact speed of an object in free fall (ignoring air resistance), using h = v₀t + ½gt². Optionally set an initial downward speed or a different gravity.
In free fall an object accelerates downward at g under gravity alone, with air resistance ignored. From a drop height h and initial downward speed v₀, the fall time is t = (−v₀ + √(v₀²+2gh))/g and the impact speed is v = √(v₀²+2gh).
Because acceleration is constant, all objects fall at the same rate regardless of mass in a vacuum — a hammer and a feather land together on the airless Moon. On other worlds simply change g (Moon 1.62, Mars 3.72 m/s²).
This is a vertical fall with constant gravitational acceleration and no air resistance. It is suitable for idealized drops near a body’s surface. It does not model terminal velocity, changing gravity over large distances, or an initial upward throw.
Height and downward speed must be non-negative; gravity must be positive. Object mass does not affect the answer in this model. Surface gravity varies by location; the Moon and Mars examples use approximate values.
For air drag, see the terminal velocity calculator. For angled launches, use the projectile motion calculator.
About 2.5 seconds. 100 ft is 30.5 m, so t = √(2·30.5/9.81) ≈ 2.49 s, ignoring air resistance, reaching roughly 24.5 m/s (55 mph) at the bottom.
For a drop from rest, v = √(2gh); with an initial speed, v = √(v₀²+2gh). It depends only on height and gravity, not on mass.
No. Ignoring air resistance, all objects fall at the same rate because gravitational acceleration is independent of mass. Differences on Earth come only from air drag.
About 9.81 m/s² at the surface (often rounded to 9.8 or 10). It varies slightly with latitude and altitude, and is much lower on the Moon (1.62 m/s²).