10-26 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} 2R&=76\ut{m}\\ T&=2\ut{min}=120\ut{s}\\ N&=60\\ \end{cases} $$ $$\text{Symmetry}\Harr\Sigma \tau=0$$ $$ \begin{aligned} W&=\int_{\theta_i}^{\theta_f}\Sigma \tau\dd\theta\\ &=\Sigma \tau\int_{\theta_i}^{\theta_f}\dd\theta\\ &=0 \end{aligned} $$