本题目来源于试卷: Space Time & Motion A.1 Kinematics，类别为 IB物理学
[单选题]
A ball rolls horizontally off the edge of the top of fch 4* yybiu46a clifht cf59w )q;zzcjr )n*f. It hits the ground at a distanz)qfwtj ; *c z)r95hcnce $2.0\,m$ from the base of the cliff with a vertical speed of $20\,m\,s^{-1}$. What is the height of the cliff?
A. $20\,m$
B. $40\,m$
C. $60\,m$
D. $80\,m$
参考答案: A
本题详细解析:
Only the vertical motion needs to be considered here.
$v^{2} = u^{2} + 2as$
$v^{2} = 2gs$
$20^{2} = (2)(10)(s)$
$s = \frac{400}{(2)(10)}$
$s = 20~m$
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