Free Fall ā Impact Speed
A ball is released from rest and falls $h = 20\ \text{m}$ to the ground. Taking
$g = 9.8\ \text{m/s}^2$ and neglecting air resistance, find its speed $v$ at impact.
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$$ v = \sqrt{2gh} $$
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m/s
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Answer
$ 19.8 m/s $
Solution
Energy conservation gives $\tfrac{1}{2}v^2 = gh$, so $v = \sqrt{2gh}$. With $g = 9.8\,$m/sĀ²
and $h = 20\,$m, $v = \sqrt{2\cdot 9.8\cdot 20} \approx 19.8\,$m/s.