Initial data: h (height from which the stone fell) = 80 m, the fall of the stone is considered free (V0 = 0 m / s).
Constants: g (acceleration due to gravity) = 10 m / s ^ 2.
1) Let’s calculate the speed of the stone before impact:
En = Ek; m * V ^ 2/2 = m * g * h; V ^ 2 = 2g * h.
V = √ (2g * h) = √ (2 * 10 * 80) = √1600 = 40 m / s.
2) Determine the flight time of the stone:
V = g * t; t = V / g = 40/10 = 4 s.
Answer: The flight time of the stone was 4 seconds, and the speed before hitting the ground was 40 m / s.
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