Science
Projectile motion
Resolve launch velocity into horizontal and vertical components to estimate projectile range, flight time and height at equal launch and landing elevations.
Calculators / Science / Free fall from rest
Free fall from rest calculator
Estimate how long an object dropped from rest takes to fall through a known height and the speed it reaches just before impact.
On this page
Fall time2.02s
Impact speed19.81m/s
Calculator controls
How to calculate
Estimate how long an object dropped from rest takes to fall through a known height and the speed it reaches just before impact.
Fall time = sqrt(2*h/g) s; Impact speed = sqrt(2*g*h) m/s
Worked example
Height (m): 20; Gravity (m/s²): 9.80665.
Fall time: 2.02 s; Impact speed: 19.81 m/s.
Assumptions and limits
Estimate how long an object dropped from rest takes to fall through a known height and the speed it reaches just before impact. Assumes constant gravity, no air resistance, and no initial vertical speed for free fall. Projectile landing height equals launch height.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Estimate how long an object dropped from rest takes to fall through a known height and the speed it reaches just before impact.
When this tool is useful
Fall time = sqrt(2*h/g) s; Impact speed = sqrt(2*g*h) m/s
Understanding your inputs
| Input | What to enter |
|---|---|
| Height (m) | Enter a number of at least 0 and no more than 1000000000000. |
| Gravity (m/s²) | Enter a number of at least 1e-12 and no more than 1000000000000. |
Frequently asked questions
What assumptions does this calculation use?
Estimate how long an object dropped from rest takes to fall through a known height and the speed it reaches just before impact. Assumes constant gravity, no air resistance, and no initial vertical speed for free fall. Projectile landing height equals launch height.
How is the result calculated?
Fall time = sqrt(2*h/g) s; Impact speed = sqrt(2*g*h) m/s