Notes

Outline

Technical Physics 1 Fluids & Pressure

Fluid Properties Density mass density (metric) weight density

Fluid Properties specific gravity - ratio of the density of the substance to the density of water adhesion - attraction between unlike molecules cohesion - attraction between like molecules surface tension - due to cohesive forces in fluid when the shape is changed capillary action - due to adhesive forces and the surface tension Viscosity - the internal resistance of a fluid

What is pressure ? Pressure is the force per unit of area within a fluid the forces are created by molecular collisions the area is the surface area of the container pressure is measured in: psi (lbs/in2) pascals (N/m2) atmospheres in.of Hg or mm of Hg

Absolute Pressure vs. Gauge Pressure Atmospheric pressure = 14.7 psi or 101.3 kPa or 1 atm. or 30 in. of Hg or 760 mm of Hg

Pressure within a fluid Pressure - may be due to the weight (density) of a fluid and the depth.

Hydraulic Press Pascal’s principle - pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of the container

Archimedes’ Principle - an object in a fluid is buoyed up with a force equal to the weight of the fluid displaced Buoyancy - apparent weight difference of an object submerged in a liquid due to the pressure difference from top to bottom

Fluid Flow Assumptions: streamline incompressible nonviscous Flow rate (R)

Continuity Constant flow rate

Bernoulli’s principle The total energy per unit of volume (pressure) of a fluid must remain constant

Special cases of Bernoulli’s equation Fluids at rest Fluid draining from large container Venturi effect