20 Solid Matter Can Experience a Shearing Stress, Liquids and Gases Cannot
A sliding stress applied to a solid deforms it to a degree which depends upon the stress and the degree of rigidity preserved by the body. Thus if the hand be placed upon a closed book lying on the table, and pressure be so applied as to move the upper side of the book but not the lower, the book is said to be subject to a shearing stress. If the pressing hand has a twisting motion, the book will be warped. Any solid may be thus sheared or warped, but neither liquids nor gases can be so affected. Molecular cohesion makes it possible in the one, and the lack of it, impossible in the others. The solid can maintain such a deformation indefinitely long, if the pressure does not rupture its molecular structure.