10-51 할리데이 11판 솔루션 일반물리학

$$ \put \begin{cases} \RE : \text{Rotational Kinetic Energy}\\ \end{cases} $$ $$ \begin{cases} \omega_0&=-4\ut{rad/s}\\ \omega_4&=8\ut{rad/s}\\ \RE_4&=2.20\ut{J}\\ \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} \alpha&=\frac{\Delta \omega}{\Delta t}\\ &=3.0\ut{rad/s^2}\\ \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} \frac{\RE_0}{\RE_4}&=\frac{\frac{1}{2}I{\omega_0}^2}{\frac{1}{2}I{\omega_4}^2}=\(\frac{\omega_0}{\omega_4}\)^2\\ \end{aligned} $$ $$ \begin{aligned} \RE_0&=\(\frac{\omega_0}{\omega_4}\)^2\cdot\RE_4\\ &=\frac{11}{20}\ut{J}\\ &=0.55\ut{J} \end{aligned} $$