To find the required time during which a given body was in free fall, we apply the formula: V = a * t = g * t, whence we express: t = V / g.
Constants and variables: V – speed of a given body at the moment of touching the ground (V = 40 m / s); g – acceleration due to gravity (g ≈ 10 m / s2).
Calculation: t = V / g = 40/10 = 4 s.
Answer: The given body should have been in free fall for 4 seconds.
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