7-23 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} F&=12.0\ut{N}\\ \theta &= 150\degree\\ m&=2.0\ut{kg}\\ \vec r&=5.00\i-6.00\j\ut{m}\\ \end{cases} $$ $$W=\vec F \cdot \vec S,$$ $$ \begin{aligned} W&=(F\cos\theta\i+F\sin\theta\j) \cdot (5\i-6\j)\\ &=12\cos150\degree\cdot5+12\sin150\degree\cdot(-6)\\ &=-36-30\sqrt3\ut{J}\\ &\approx -87.96152422706632\ut{J}\\ &\approx -88\ut{J}\\ \end{aligned} $$