The natural frequency of simple pendulum with a length equal to the earth’s radius. The corresponding period is 84 minutes.
Related Terms 
PLAN EQUATION
The mathematical statement that horsepower plan/33,000, where p mean effective pressure (pounds per square inch), l length of piston stroke (feet), a net area of piston (square inches), and n number of cycles completed per minute.

OVERDRILLING
The act or process of drilling a run or length of borehole greater than the corecapacity length of the core barrel, resulting in loss of the core.

OSTWALD VISCOMETER
A viscometer in which liquid is drawn into the higher of two glass bulbs joined by a length of capillary tubing, and the time for its meniscus to fall between calibration marks above and below the upper bulb is compared with that for a liquid of known viscosity.

ORIGINALDURATION
[INDENG] The initial estimate of length of time required to complete a given activity.

NYQUIST CONTOUR
A directed closed path in the complex frequency plane used in constructing a Nyquist diagram, which runs upward, parallel to the whole length of the imaginary axis at an infinitesimal distance to the right of it, and returns from jn to jn along a semicircle of infinite radius in the right halfplane.

NUSSELT NUMBER
A dimensionless number used in the study of forced convection which gives a measure of the ratio of the total heat transfer to conductive heat transfer, and is equal to the heattransfer coefficient times a characteristic length divided by the thermal conductivity. Symbolized NNu.

NAUTICAL CHAIN
A unit of length equal to 15 feet or 4.572 meters.

MODULAR STRUCTURE
1. A building that is constructed of preassembled or presized units of standard sizes; uses a 4inch (10.16centimeter) cubical module as a reference. 2. An assembly involving the use of integral multiples of a given length for the dimensions of electronic components and electronic equipment, as well as for spacings of holes in a chassis or printed wiring board. 3. An assembly made from modules.

MILLIMETER
A unit of length equal to onethousandth of a meter. Abbreviated mm. Also known as metric line; strich.

METER WHEEL
A special block used to support the oceanographic wire paid out over the side of a ship; attached directly or connected by means of a speedometer cable to a gearbox which measures the length of wire.
