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Coefficient of sliding friction FT / FN versus normalized velocity, U* = μU / rFN, for elastic V blocks (light lines with V label) and elastic Q blocks (bold lines with Q label). These are shown as a family in material stiffness Φ of the blocks given by Φ / FN = 3.0 (solid line), 1.0 (dotted line), and 0.3 (dashed line). Surface roughness is given by r = 0.2 . At fixed U *, the friction coefficient increases with increasing material stiffness.
