A stone is dropped from a height of 20 m. Ignoring air resistance and taking g = 9.8 m/s², what is its speed just before hitting the ground?
Correct answer A. 19.8 m/s
Explanation
Energy conservation: mgh = ½mv², so v = √(2gh) = √(2 × 9.8 × 20) = √392 = 19.8 m/s. Forgetting the square root gives 392.
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