In a vacuum every object falls identically and two equations settle it. Add air and neither holds — but they remain the right starting point, and the gap between them and the simulation is the effect of drag.
In a vacuum h = ½gt², so t = √(2h/g) and v = √(2gh). Mass appears in neither: every object falls the same way.
Drag scales with cross-sectional area, inertia with mass. A feather has enormous area for its mass; a hammer has so much mass for its area that drag barely matters over a short drop.
Drag grows with v² until it cancels weight: vt = √(2mg / ρCdA). Falling further adds time, not speed.
Over 1.6 m a ping-pong ball has barely felt the air; over 56 m it has long hit terminal velocity. Same objects, opposite impressions.
Gravitational acceleration does not depend on what an object is made of or how much it weighs: a consequence of gravitational and inertial mass being the same thing, tested to extraordinary precision by modern experiments, not just dropped hammers.
The ratio of mass to (drag coefficient × area) decides how much air matters: a high ratio (dense, streamlined) barely notices air; a low one (light, spread out) is dominated by it at once. Terminal velocity is reached asymptotically: about 95% within a few seconds for most everyday objects. A feather is there almost instantly; a dense hammer from a short drop never gets close. The tool reports what fraction of terminal velocity each object has at impact.
In a vacuum a hammer and a feather land together. In air a heavier object usually lands first, but through its higher terminal velocity: more mass per unit of frontal area means drag takes longer to catch up. Drag goes as v² because faster motion pushes more air out of the way per second and pushes it away faster.
No atmosphere means zero drag on anything at any speed: the Moon is a giant free vacuum chamber. Commander David Scott dropped a geology hammer and a falcon feather on live television on 2 August 1971 and they landed together. Mars’s atmosphere is roughly 1.6% as dense as Earth’s: present enough for dust storms, far too thin to slow a dense object over a short drop.
Almost certainly not literally: it is a story told by his student Viviani decades later, with no confirmation in Galileo’s own writing. What is documented is his careful reasoning and rolling-ball experiments on inclined planes that falling bodies accelerate independently of mass.
Almost certainly not literally — it's a story told by his student Viviani, decades later, with no confirmation in Galileo's own writing. What's well documented is Galileo's careful reasoning (and rolling-ball experiments on inclined planes) that falling bodies accelerate independent of mass, which is the actual physics this tool demonstrates.
Yes — Commander David Scott dropped a geology hammer and a falcon feather on live television on August 2, 1971, and they landed together, exactly as Galileo's physics predicted. It remains one of the most direct public demonstrations of the equivalence principle ever performed.
In a vacuum, t = √(2h/g) — about 0.45 s from 1 m on Earth, 1.43 s from 10 m,
4.52 s from 100 m. Impact speed is v = √(2gh). Mass is in neither equation. With air,
those times are a floor: the tool shows both so you can see what the drag actually costs.
Not because it is heavier. In a vacuum, no — a hammer and a feather land together. In air, a heavier object usually lands first, but the reason is its higher terminal velocity: more mass per unit of frontal area means drag takes longer to catch up with weight. Mass matters only through that ratio.
vt = √(2mg / ρCdA). An object approaches it asymptotically, so
"reached" means close enough — around 95% within a few seconds for most everyday objects. The tool
reports what fraction of terminal velocity each object has at impact, which tells you whether the drop
was long enough for air to matter at all.
Faster motion pushes more air out of the way per second and pushes it away faster — both effects scale with speed, so the combined drag force scales with speed squared. It's why terminal velocity exists at all: drag grows quadratically until it exactly cancels gravity.
Mars's atmosphere is roughly 1.6% as dense as Earth's at the surface — present enough for dust storms, far too thin to meaningfully slow a dense object over a short drop. It's a genuine middle ground between Earth's air and the Moon's true vacuum.
Releases in which this page changed, newest last. Derived from the archived copy of every release, not from notes written afterwards — so it reflects what actually shipped. Site-wide passes are left out; they are in the full changelog.