Free Fall Calculator
A stone dropped from 45 m falls for 3.02943 s before it lands, at about 29.7 m/s (107 km/h), ignoring air resistance.
From rest, no air resistance. Moon 1.62, Mars 3.71 m/s².
3.02942996565383 s
Full answer, then cut to fewer decimals (not rounded):
- 3.02942996565383 s
- 3.0294299656538 s
- 3.029429965653 s
- 3.02942996565 s
- 3.0294299656 s
- 3.029429965 s
- 3.02942996 s
- 3.0294299 s
- 3.029429 s
- 3.02942 s
- 3.0294 s
- 3.029 s
- 3.02 s
- 3.0 s
- Impact speed v = gt
- 29.70855937 m/s
- Impact speed
- 106.9508137 km/h
- Impact speed
- 66.45615465 mph
- Average speed h/t
- 14.85427969 m/s
Step-by-step solution
- t = √(2h ÷ g) = √(2 × 45 ÷ 9.80665)
- t = 3.029429966 s
- v = g × t = 9.80665 × 3.029429966 = 29.70855937 m/s
Free Fall Formula
h = ½ g t², v = g t = √(2gh)
h height fallen, t time, v speed reached, g gravitational acceleration
Worked Example
A stone dropped from 45 m:
- t = √(2h ÷ g) = √(2 × 45 ÷ 9.80665)
- t = 3.029429966 s
- v = g × t = 9.80665 × 3.029429966 = 29.70855937 m/s
Impact speed: 106.9508137 km/h · Impact speed: 66.45615465 mph · Average speed h/t: 14.85427969 m/s
Estimating a cliff’s height
Drop a stone and time the fall: 2 s means about 19.6 m, 3 s about 44 m. Sound takes about 0.13 s to come back up 45 m, so subtract a little for tall drops.
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Frequently asked questions
Does a heavier object fall faster?
Not in a vacuum: all objects fall with the same acceleration g. In air, drag slows light or broad objects more, which is why a feather lags a hammer on Earth but not on the Moon.
What is terminal velocity?
The speed where air drag balances weight, so acceleration stops. A skydiver reaches about 55 m/s (200 km/h) belly-down; this calculator ignores drag and is accurate only for short, dense falls.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Free Fall Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/free-fall-calculator/
IEEE
Scientific Converters, "Free Fall Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/free-fall-calculator/