質量行列
q = [ x 1 x 2 ] T {\displaystyle q={\begin{bmatrix}x_{1}&x_{2}\end{bmatrix}}^{\textsf {T}}} 。
T = ∑ i = 1 2 1 2 m i x i ̇ 2 {\displaystyle T=\sum _{i=1}^{2}{\frac {1}{2}}m_{i}{\dot {x_{i}}}^{2}}
T = 1 2 q ̇ T M q ̇ {\displaystyle T={\frac {1}{2}}{\dot {q}}^{\textsf {T}}M{\dot {q}}}
M = [ m 1 0 0 m 2 ] {\displaystyle M={\begin{bmatrix}m_{1}&0\\0&m_{2}\end{bmatrix}}}