91Ó°ÊÓ

• The total mass is M
• The Length of each member (horizontal and vertical member) is L

The center of mass of the system is calculated by considering the average positions of all the objects acting in the system.

For the first origin (one in the lower left corner at the intersection of the horizontal and vertical members), the diagram will be the following,

The center of mass of the system,

$$\begin{gathered} \mathit{M}{\mathit{x}}_{\mathbf{C}\mathbf{M}}\mathbf{=}{\mathit{m}}_{\mathbf{1}}{\mathit{x}}_{\mathbf{1}}\mathbf{+}{\mathit{m}}_{\mathbf{2}}{\mathit{x}}_{\mathbf{2}} \\ \mathit{M}{\mathit{y}}_{\mathbf{C}\mathbf{M}}\mathbf{=}{\mathit{m}}_{\mathbf{1}}{\mathit{y}}_{\mathbf{1}}\mathbf{+}{\mathit{m}}_{\mathbf{2}}{\mathit{y}}_{\mathbf{2}} \end{gathered}$$

Here,

$$\begin{gathered} m_1=m_2=M \\ {M}_{total}=2M \\ \left(x_1,y_1\right)=\left(L/2,0\right) \\ \left(x_2,y_2\right)=\left(0,L/2\right) \end{gathered}$$

Substitute these values in Equation (1),

To find x coordinate.

$$\begin{gathered} 2M.x_{CM}=M.L/2+M.0 \\ 2M.x_{CM}=M.L/2 \\ {x}_{CM}=L/4 \end{gathered}$$

To find y coordinate,

$$\begin{gathered} M{y}_{CM}=m_1{y}_1+m_2{y}_2 \\ 2M.y_{CM}=M.0+M.L/2 \\ 2M.y_{CM}=M.L/2 \\ {y}_{CM}=L/4 \end{gathered}$$

Hence, the coordinate of center of mass is$\left(L/4,L/4,0\right)$

For the second origin (at the right end of the horizontal member), the diagram will be the following,

$$\begin{gathered} \mathit{M}{\mathit{x}}_{\mathbf{CM}}\mathbf{=}{\mathit{m}}_{\mathbf{1}}{\mathit{x}}_{\mathbf{1}}\mathbf{+}{\mathit{m}}_{\mathbf{2}}{\mathit{x}}_{\mathbf{2}} \\ \mathit{M}{\mathit{y}}_{\mathbf{CM}}\mathbf{=}{\mathit{m}}_{\mathbf{1}}{\mathit{y}}_{\mathbf{1}}\mathbf{+}{\mathit{m}}_{\mathbf{2}}{\mathit{y}}_{\mathbf{2}} \end{gathered}$$

Here,

$$\begin{gathered} m_1=m_2=M \\ {M}_{total}=2M \\ \left(x_1,y_1\right)=\left(-L/2,0\right) \\ \left(x_2,y_2\right)=\left(0,L/2\right) \end{gathered}$$

Substitute these values in Equation (1),

To find x coordinate.

$$\begin{gathered} 2M.x_{CM}=M.\left(-L/2\right)+M.0 \\ 2M.x_{CM}=-M.L/2 \\ {x}_{CM}=-L/4 \end{gathered}$$

To find y coordinate,

$$\begin{gathered} M{y}_{CM}=m_1{y}_1+m_2{y}_2 \\ 2M.y_{CM}=M.0+M.L/2 \\ 2M.y_{CM}=M.L/2 \\ {y}_{CM}=L/4 \end{gathered}$$

Hence, the coordinate of center of mass is$\left(-L/4,L/4,0\right)$