\(\dfrac{W_1}{W_2}=\dfrac{\dfrac{1}{2}m\omega^2A_1^2}{\dfrac{1}{2}m\omega^2A_2^2}=\dfrac{A_1^2}{A^2_2}=\dfrac{(3A)^2}{A^2}=9\Rightarrow W_1=9W_2\\\dfrac{W_{t_1}}{W_{t_2}}=\dfrac{\dfrac{1}{2}m\omega^2x_1^2}{\dfrac{1}{2}m\omega^2x_2^2}=\dfrac{x_1^2}{x^2_2}=\dfrac{[3A\cos(\omega t+\varphi)]^2}{[A\cos(\omega t+\varphi)]^2}=9\Rightarrow W_{t_1}=9W_{t_2}\)

Khi `W_(d_1)=6(mJ),W_(t_2)=4/3(mJ)`

\(\Rightarrow \begin{cases}W_{t_1}=9W_{t_2}=12(mJ)\\W_1=W_{d_1}+W_{t_1}=6+12=18(mJ)\Rightarrow W_2=2(mJ)\end{cases}\)

Khi `W_(t_1)=9(mJ)=>W_(t_2)=1(mJ)`

\(W_2=2(mJ)=W_{d_2}+W_{t_2}\Rightarrow W_{d_2}=1(mJ)\\\longrightarrow C.\)