11-37 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} \vec F&=-8.0\i+4.0\j\ut{N}\\ \vec r&=3.0\i+4.0\j\ut{m}\\ \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} \vec \tau &= \vec r\times \vec F,\\ &=44\k\ut{N\cdot m} \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} \abs{\vec r\times \vec F} &= rF\sin\phi,\\ \phi &=\sin^{-1}{\abs{\vec r\times \vec F}\over rF}\\ &=\sin^{-1}{44\over 5\cdot4\sqrt5}\\ &\approx 1.390942827002419\ut{rad}\\ &\approx 1.4\ut{rad}\\ \end{aligned} $$