Instructions.
Interactive shows the moment
\begin{equation*}
\vec{M} = \vec{r} \times \vec{F}
\end{equation*}
about an arbitrary point \(A\text{.}\) Force \(\vec{F}\) is defined by a scalar magnitude \(F\) and two points on its line of action, \(P_1\) and \(P_2\text{.}\) Position vector \(\vec{r}\) is the displacement from point \(A\) to a point on the line of action.
The locations of \(A\text{,}\) \(P_1\text{,}\) \(P_2\) and magnitude \(F\) can be set interactively. The interactive determines the components of \(\vec{r}\text{,}\) the unit vector \(\lambda\) of the line of action, and the components of \(\vec{F}\) and \(\vec{M}\text{.}\)
Note that sliding vector \(\vec{F}\) or the tip of vector \(r\) along the line of action has no effect on the resulting moment \(\vec{M}\text{.}\)
The magnitude of the moment can be visualized as the area of a parallelogram with sides \(r\) and \(F\text{.}\)