Momentum–depth relationship in a rectangular channel Momentum–depth relationship in a rectangular channel In classical physics, momentum is the product of mass and velocity and is a vector quantity, but in fluid mechanics it is treated as a longitudinal quantity (i.e. one dimension) evaluated in the direction of flow. Additionally, it is evaluated as momentum per unit time, corresponding to the product of mass flow rate and velocity, and therefore it has units of force. The momentum forces considered in open channel flow are dynamic force – dependent of depth and flow rate – and static force – dependent of depth – both affected by gravity. The
Law of mass action formula. The law of mass action also has implications in semiconductor physics. Regardless of doping, the product of electron and hole densities is a constant at equilibrium. This constant depends on the thermal energy of the system (i.e. the product of the Boltzmann constant, formula_20, and temperature, formula_21), as well as the band gap (the energy separation between conduction and valence bands, formula_22) and effective density of states in the valence formula_23 and conduction formula_24 bands. When the equilibrium electron formula_25 and hole formula_26 densities are equal, their density is called the "intrinsic" carrier density formula_27 as this would be