Free Fall Calculator
Enter height, fall time or impact speed to get the other two. h = ½ g t², v = g t. Air resistance is neglected.
What is free fall?
Free fall is the motion of an object dropped from rest under gravity alone. With air resistance neglected, every object speeds up at the same rate whatever its mass: g = 9.81 m/s².
Formulas
- Height fallen: h = ½ × g × t²
- Speed: v = g × t
- Speed from height: v = √(2 × g × h)
- Time from height: t = √(2 × h / g)
Mass does not appear in the formulas. In a vacuum a hammer and a feather hit the ground together.
Example
An object released from 20 metres reaches the ground in t = √(2 × 20 / 9.80665) = 2.02 seconds. Its impact speed is v = √(2 × 9.80665 × 20) = 19.8 m/s, about 71 km/h.
Limits
The calculation ignores air resistance. For short drops and dense objects (a stone, a steel ball) the result is very close to reality. For paper, feathers or parachutes, and for drops of more than a few tens of metres, the real speed is lower. The tool does not give the force at impact, which depends on the stopping distance.
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