Thursday 6/18 PHYS 2010 Nathalie Hoffmann University of Utah Gauge Pressure • ๐ − ๐0 = ๐๐๐ข๐๐ ๐๐๐๐ ๐ ๐ข๐๐ • ๐0 is the absolute pressure • Gauge pressure shows how much the pressure exceeds atmospheric pressure/absolute pressure Archimedes’ Principle • The buoyant force on an object immersed in a fluid is equal to the weight of the fluid that the object displaces. Volume Flow Rate (Q) • Equation of Continuity: • ๐1 = ๐2 = ๐๐๐๐ ๐ก๐๐๐ก •๐= ΔV Δt • (flow rate gives the volume of fluid passing a certain point in a given time interval) • ๐ = ๐ด๐ฃ Steady vs. Unsteady Flow • Steady flow: the flow pattern at any given point does not change with time, at any given point the flow velocity remains constant with time; does not mean the flow velocity is constant everywhere • Unsteady flow: the flow velocity at a given point can change with time Laminar vs. Turbulent Flow • Laminar flow: each bit of fluid follows a path called a streamline, which do not cross • Turbulent flow: no streamlines, adjacent bits of fluid can follow very different paths Viscosity • Viscosity is an intrinsic resistance to flow. Because adjacent parts of a fluid move at different velocities, the parts rub and exert frictional forces on each other. Bernoulli’s Principle • In a moving fluid, the pressure is low where the fluid is moving rapidly • ๐1 + 1 ๐๐ฃ12 2 + ๐๐๐ฆ1 = ๐2 + 1 ๐๐ฃ22 2 + ๐๐๐ฆ2 • Assumptions: steady, laminar flow Bernoulli’s Principle • In a moving fluid, the pressure is low where the fluid is moving rapidly • ๐1 + 1 ๐๐ฃ12 2 + ๐๐๐ฆ1 = ๐2 + 1 ๐๐ฃ22 2 + ๐๐๐ฆ2 • Assumptions: steady, laminar flow