3-44 할리데이 11판 솔루션 일반물리학

$$\begin{cases} \vec r &= \(5.25\i+4.90\j+3.00\k\)\ut{m} \end{cases}$$ $$\ab{a}$$ $$\begin{aligned} r &= \sqrt{5.25^2+4.9^2+3^2}\\ &=\frac{1}{20}\sqrt{24229}\ut{m}\\ &\approx 7.782833674183202\ut{m}\\ &\approx 7.78\ut{m}\\ \end{aligned}$$ $$\ab{b}$$ $$l\lt r ~?$$ $$\title{Impossible}$$ $$\ab{c}$$ $$l\gt r ~?$$ $$\title{Possible}$$ $$\ab{d}$$ $$l = r ~?$$ $$\title{Possible}$$ $$\ab{e}$$ $$\vec r = \(5.25\i+4.90\j+3.00\k\)\ut{m}$$ $$\ab{f}$$ $$\begin{aligned} l_1 &= \sqrt{5.25^2+(4.90+3)^2}\\ &=\frac{\sqrt{35989}}{20}\\ l_2 &= \sqrt{3^2+(5.25+4.90)^2}\\ &=\frac{\sqrt{44809}}{20}\\ l_3 &= \sqrt{4.90^2+(3+5.25)^2}\\ &=\frac{\sqrt{36829}}{20}\\ \end{aligned}$$ $$\begin{aligned} l_{\min}&=l_1 \\ &= \frac{\sqrt{35989}}{20}\\ &\approx 9.48538349251099\ut{m}\\ &\approx 9.49\ut{m}\\ \end{aligned}$$