12-34 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} m_A&=10\ut{kg}\\ m_B&=5.0\ut{kg}\\ \theta&=30\degree \end{cases} $$ $$0=\vec F_A+\vec F_B+\vec T,$$ $$ \begin{aligned} \tan\theta&={F_A\over F_B}\\ &={\mu m_Ag\over m_Bg}\\ \end{aligned} $$ $$ \begin{aligned} \mu&={m_B\over m_A}\tan\theta\\ &={1\over2\sqrt3}\\ &\approx 0.2886751345948129\\ &\approx 0.29\\ \end{aligned} $$