本题目来源于试卷: 2012美国US F=MA物理竞赛，类别为 美国F=MA物理竞赛
[单选题]
The softest audible sup bxs, c*sy:0ojh,: afk:/fv nund has an intensity of $I_{0}=10^{-12} W/m^{2}$. In terms of the fundamental units of kilograms, meters, and seconds, this is equivalent to
A. $I_{0}=10^{-12} kg/s^{3}$
B. $I_{0}=10^{-12} kg/s$
C. $I_{0}=10^{-12} kg^{2} m/s$
D. $I_{0}=10^{-12} kg^{2} m/s^{2}$
E. $I_{0}=10^{-12} kg/m \cdot s^{3}$
参考答案: A
本题详细解析:
Intensity $I$ has units of Power / Area, or $W/m^2$.
Power $P$ (Watts) is Energy / time, or $J/s$.
Energy $E$ (Joules) is Force $\times$ distance, or $N \cdot m$.
Force $F$ (Newtons) is mass $\times$ acceleration, or $kg \cdot m/s^2$.
Substituting back:
$F \rightarrow kg \cdot m/s^2$
$E \rightarrow (kg \cdot m/s^2) \cdot m = kg \cdot m^2/s^2$
$P \rightarrow (kg \cdot m^2/s^2) / s = kg \cdot m^2/s^3$
$I \rightarrow (kg \cdot m^2/s^3) / m^2 = kg/s^3$.
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