Surface Tension
"The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. The molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. This forms a surface "film" which makes it more difficult to move an object through the surface than to move it when it is completely submersed".
Surface tension is typically measured in dynes/cm, the force in dynes required to break a film of length 1 cm. Equivalently, it can be stated as surface energy in ergs per square centimeter. Water at 20°C has a surface tension of 72.8 dynes/cm compared to 22.3 for ethyl alcohol and 465 for mercury.
Hydrostatics is defined as that branch of physics, which has to do with the pressure and equilibrium of water and other liquids. Liquids at rest present far simpler problems to solve than those of fluid dynamics, since individual fluid elements do not move relative to others in the fluid body, therefore shear forces are not involved and all pressure forces are normal to the fluid elements surfaces. Following the criteria that fluid elements should not move relative to one another, hydrostatics can be extended to systems of relative equilibrium , where elements have no relative motion although the body of liquid may be moving as a whole. The following will be briefly described: pressure variation in compressible and incompressible liquids; forces on planes; stability of floating and submerged bodies; relative equilibrium; and manometry.
Hydrodynamics:-"The scientific study of the motion of fluids, especially noncompressible liquids, under the influence of internal and external forces. Hydrodynamics is a branch of fluid mechanics and has many applications in engineering. Compare aerodynamics hydrostatics"
Vectors: "A vector is a quantity or phenomenon that has two independent properties: magnitude and direction. The term also denotes the mathematical or geometrical representation of such a quantity. Examples of vectors in nature are velocity, momentum, force, electromagnetic fields, and weight".
Comments
Post a Comment