This model extends the three-force model by providing for moving the torque axis off the center of mass. You may adjust the applied forces or clear the vectors for repositioning as in the three-force model. At any point you may relocate the torque axis by clicking the mouse while holding down the Alt key.

We have added the moment arms for the force vectors to make clearer the role of the torque axis. To eliminate some clutter, the vector lines of action and the reaction force radius have been removed. The reaction radius label remains so that the location of he reaction force attachment point is indicated when the reaction vector may be off-screen. The last line written on the drawing area lists the torque about the center of mass for each of the force vectors, applied force 1, applied force 2 and reaction force, respectively. These values are calculated independently, rather than forcing TR = -(T1+T2). If you check closely, you may see minor departures from zero for T1 + T2 + TR, due to calculation precision.

For details on the operation of controls, see the Model Controls help page.