, to the normal to the wall, and the thrust [is]:
The foregoing constructions, and the corresponding equations, are all derived from the theory of the sliding prism. The wedge,
, [Figs. 2] and 3, is treated as an invariable solid, tending to slide down the two faces,
and
, at once, thus developing the full friction that can be exerted on these faces. In the case of actual rotation of the board,