A pressure differential between the outside and the inside causes the cylinder to expand or contract axially. The force that tends to draw all bodies toward the center of the earth. The weight of a body is the resultant of gravitational force acting on the body. The height of a column or body of fluid above a given point expressed in linear units. Head is often used to indicate gauge pressure.
Pressure is equal to the height times the density of the fluid.
The head required to overcome the friction at the interior surface of a conductor and between fluid particles in motion. The equivalent head through which the liquid would have to fall to attain a given velocity. An instrument for deter-mining the specific gravities of liquids. The striking or dashing upon with a clash or sharp collision, as air impinging upon the rotor of a turbine or motor. A turbine driven by a fluid at high velocity under relatively low pressure.