How this calculator works
A released ruler accelerates from rest. The distance it falls before being caught corresponds to the total interval from release to capture. Each trial is converted separately before taking the mean; converting the mean distance would give a different value. The sample standard deviation is reported only with at least two trials. Air resistance, anticipation and the time to close fingers make this an approximate experiment rather than a diagnostic test.
Formula
d = gt²/2; t = sqrt(2d/g). Mean time = sum(ti)/N; sample standard deviation uses N-1.
Worked example
At g = 10 m/s2, drops of 0.2 m and 0.45 m correspond to 0.2 s and 0.3 s. Their mean interval is 0.25 s.
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Frequently asked questions
Why not average the distances first?
Time depends on the square root of distance. Transforming each trial before averaging gives the mean measured interval.
Is this a medical reaction-time assessment?
No. It is a simple free-fall experiment that includes sensory, decision and capture delays.
Can I enter more than five trials?
Yes. The list accepts up to 100 non-negative trials.