4-20 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} r&=4.20\ut{m}\\ \vec a &=\(6.00\i-5.20\j\)\ut{m/s^2}\\ \end{cases} $$ $$\ab{a}$$ $$\vec v \cdot \vec a=0$$ $$\because~\vec v \perp\vec a$$ $$\ab{b}$$ $$\vec r \times \vec a = 0$$ $$\because~\vec r \parallel \vec a$$