Initial data: h (height from which the stone fell freely) = 20 m.
Reference data: according to the condition g (gravitational acceleration) = 10 m / s2.
We express the time when the stone in question reaches the ground from the formula: S = h = g * t ^ 2/2, whence t ^ 2 = 2 * h / g and t = √ (2 * h / g).
Calculation: t = √ (2 * 20/10) = √4 = 2 s.
Answer: When free falling, the stone in question will fall to the ground in 2 seconds.
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