In this display, the first click on the mouse button fixes the vector r from the origin to the particle. Then dragging the cursor around the point of the r vector where the particle is located, adjusts the direction and magnitude of the force vector f.
The distance from the origin of the reference frame to the line of action of the force vector is called the "moment arm" of the force vector. The magnitude of the torque is the length of the force vector times the length of the moment arm. On the display, the line of action of the force vector is shown in gray if required and the moment arm is shown in yellow. The magnitude and direction of the torque vector is displayed in text form on the display. The particle is shown as a light blue ball and the origin of the coordinate system is marked by a white cross.