ABSTRACT
Pressure is defined as the normal force per unit area exerted by a fluid on any surface. The surface can be either a solid boundary in contact with the fluid or, for purposes of analysis, an imaginary plane drawn through the fluid. Tangential forces that give rise to shear and fluid motion will not be a relevant subject of discussion here. In the limit that the surface area approaches zero, the ratio of the differential normal force to the differential area represents the pressure at a point on the surface. Ultrasound has a broad range of applications in medicine, where it is referred to as medical ultrasound. It is widely used in obstetrics to follow the development of the fetus during pregnancy, in cardiology where images can display the dynamics of blood flow and the motion of tissue structures, and for locating tumors and cysts.
