Axial () and lateral () force components at the whisker base were calculated, in each video frame where there were whisker-pole contacts, as follows (Pammer et al., 2013). First, the point of whisker-pole contact was located (Materials and methods). The direction of the force was then calculated as the normal to the whisker tangent at the contact point (Pammer et al., 2013). Moment at the base M was calculated from the whisker curvature at the base (Materials and methods) and then the magnitude F of was derived from the definition of moment:
where r is the magnitude of the lever arm vector from whisker base to contact point, and φ is the angle between and . The components Fax and Flat were then found by projecting onto the tangent and normal to the whisker at its base, respectively:
Here is the angle between the tangent to the whisker at its base and the horizontal; is the angle between and the horizontal.