Free Fall Calculator

Use constant-gravity kinematics to estimate fall time and impact speed while explicitly excluding air resistance.

Fall height

Initial downward speed

Gravitym/s²

—Fall time

—Impact speed m/s

—Impact km/h

—Impact mph

—No air resistance; constant gravity.

These are idealized classical-physics calculations. Real systems can differ because of air resistance, friction, deformation, measurement uncertainty, non-constant forces, or other effects not included in the selected model.

Physics model preflight

Check the governing model before trusting the number

constant gravity, no drag

h = v₀t + ½gt²

Reading the current native inputs…

Height and downward initial speed are non-negative; g must be positive. Drag is excluded. This is an idealized educational model: unit consistency and valid inputs do not guarantee that omitted effects are negligible in a real system.

Ideal vs linear-drag comparison

Keep the textbook constant-g result, then compare an optional linear-drag model to show terminal-speed and model sensitivity.

Physics evidence

Mass (kg)

Linear drag k (kg/s)

Comparison

Model	Impact time	Impact speed	Boundary

Use the tool above, then refresh this verification.

Verification uses the visible inputs and keeps the original tool workflow intact.

State the model before trusting the number

Classical formulas are only as good as their assumptions and units. Air resistance, damping, deformation, non-constant forces and measurement uncertainty are not silently invented when the selected model does not include them.

Governing physics model

h = v₀t + ½gt² — constant gravity, no drag.

How to verify the result

For zero initial downward speed, h should equal ½gt² and impact speed should equal gt. Lower gravity should increase fall time.

Domain and assumption boundary

Height and downward initial speed are non-negative; g must be positive. Drag is excluded. The calculator does not silently add drag, damping, deformation, varying fields, relativistic effects, measurement uncertainty, or geometry that the selected model does not contain.

Practical guide and verification

Use the tool above first. These notes explain how to interpret, verify and bound the result without displacing the primary workflow.

State the physical model first

The familiar free-fall equations assume constant gravitational acceleration and usually neglect air resistance. That model is useful for short textbook-style motions, but real objects can depart from it when drag, buoyancy or changing gravity become significant.

Initial velocity changes the trajectory

Dropping an object from rest is only one case. A nonzero downward initial velocity adds a linear v₀t term to displacement, while an upward initial velocity changes the early part of the motion before gravity reverses the direction.

Common mistake

Do not mix sign conventions midway through the calculation. Decide whether downward is positive or negative, keep acceleration and initial velocity consistent with that choice, and interpret the final velocity with the same convention.

Verification

For a drop from rest under constant g, check that distance follows one-half g times time squared and final speed follows g times time. Substituting the calculated time into both relationships should reproduce the entered height and the reported velocity within rounding.

Domain boundary

Large heights, very light objects, parachutes and high-speed motion can require drag models or changing gravity. The optional drag comparison is a model illustration rather than a universal prediction of a real object without measured drag parameters.