\(l_{min}=8cm\)
\(l_{max}=16cm\)
Biên độ: \(A=\dfrac{l_{max}-l_{min}}{2}=4cm\)
Cơ năng: \(W=\dfrac{1}{2}kA^2=\dfrac{1}{2}.16.(0,04)^2=0,0128J\)
Khi vật cách VTCB 2cm thì: \(\dfrac{W_t}{W}=(\dfrac{2}{4})^2=\dfrac{1}{4}\)
\(\Rightarrow W_t=\dfrac{W}{4}=\dfrac{0,0128}{4}=0,0032(J)\)