Abstract: The isolated system solid / liquid / steam should be considered as a kind of a mechanical system based on the interaction of the forces acting in the system. Within this concept and with the involvement of molecular-kinetic theory the author considered force characteristics at the interface when wetting low-energy smooth solid surfaces. It is shown that the magnitude of the adhesion forces occurring upon wetting between particles (molecules) of liquid placed on a three-phase contact line, and particles on the surface of the solid depends on the surface energy characteristics of a solid body and a liquid. The resulting new equation (Young-Verkholomov equation) of the equilibrium contact angle is

Cosθ₀ = (σ_A - σ_LS) / σ_LV,

where σ_A - the adhesive force at the interface solid/vapor;

σ_LS, σ_LV - surface tension of liquid at the interface liquid / solid phase, and liquid / vapor respectively.