5-58 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} \vec a&=3.0\j\ut{m/s^2}\\ m&=3.0\ut{kg}\\ \vec F_1&=8.0\i\ut{N} \end{cases} $$ $$\Sigma \vec F = m\vec a,$$ $$ \begin{aligned} \vec F_1+\vec F_2 &= m \vec a\\ \vec F_2&=m \vec a-\vec F_1\\ &=9\j-8\i\ut{N}\\ \end{aligned} $$ $$ \begin{aligned} F_2&=\sqrt{9^2+8^2}\\ &=\sqrt{145}\ut{N}\\ &\approx 12.041594578792296\ut{N}\\ &\approx 12\ut{N}\\ \end{aligned} $$