Free fall

Free fall is motion under gravity alone, with zero initial velocity. It is governed by the formulas (for $g=9.81\ \tfrac{\text{m}}{\text{s}^2}$):

$v=g\,t\qquad h=\tfrac12\,g\,t^2\qquad v^2=2\,g\,h$

Enter one known quantity — the fall time, the height or the final velocity — and the calculator works out the rest. In a vacuum all bodies fall equally fast, regardless of mass (as shown by the feather-and-hammer experiment on the Moon).