10-1 할리데이 11판 솔루션 일반물리학

$$ \begin{cases} m_1&=70.0\ut{kg}\\ I_1&=12.0\ut{kg\cdot m^2}\\ x_1 &= 3.0\ut{cm}=3.0\times10^{-2}\ut{m}\\ g&=9.80665\ut{m/s^2} \end{cases} $$ $$\ab{a}$$ $$ \begin{aligned} \tau_1 &= r_\perp F,\\ &= +x_1 m_1g\\ &=2.1g \end{aligned} $$ $$\Sigma \tau =I\alpha,$$ $$ \begin{aligned} \alpha &=\frac{\tau_1}{I}\\ &=\frac{7}{40}g\\ &=1.71616375\ut{rad/s^2}\\ &\approx 1.7\ut{rad/s^2}\\ \end{aligned} $$ $$\ab{b}$$ $$ \begin{aligned} \tau_2 &= r_\perp F,\ut{kg m^2/s^2}\\ &= -x_2 m_2g\\ &=-\frac{28}{25}g \end{aligned} $$ $$I=\Sigma mr^2,$$ $$ \begin{aligned} I_2&=m_2{x_2}^2\\ &=\frac{56}{625}\ut{kg\cdot m^2} \end{aligned} $$ $$ \begin{aligned} \alpha &=\frac{\tau_1-\tau_2}{I_1+I_2}\\ &= \frac{1225}{15112}g\\ &\approx 0.7949408582583377\ut{rad/s^2}\\ &\approx 0.79\ut{rad/s^2}\\ \end{aligned} $$