about an axis
121To turn about — Turn Turn, v. i. 1. To move round; to have a circular motion; to revolve entirely, repeatedly, or partially; to change position, so as to face differently; to whirl or wheel round; as, a wheel turns on its axis; a spindle turns on a pivot; a man… …
122polar axis — /poʊlər ˈæksəs/ (say pohluhr aksuhs) noun a line about which a body rotates, or about which a rotation is measured …
123principal axis — 1. Optics. a line passing through the center of the surface of a lens or spherical mirror and through the centers of curvature of all segments of the lens or mirror. 2. Physics. one of three mutually perpendicular axes of a body about which the… …
124long axis of body — the imaginary straight line projected on the median plane through the neck, thorax, abdomen, and pelvis about which the weights of the torso are most symmetrically distributed …
125two-axis tracking — A system capable of rotating independently about two axes (e.g., vertical and horizontal) and following the sun for maximum efficiency of the solar array. Solar Electric Glossary …
126Moment of inertia — This article is about the moment of inertia of a rotating object, also termed the mass moment of inertia. For the moment of inertia dealing with the bending of a beam, also termed the area moment of inertia, see second moment of area. In… …
127mechanics — /meuh kan iks/, n. 1. (used with a sing. v.) the branch of physics that deals with the action of forces on bodies and with motion, comprised of kinetics, statics, and kinematics. 2. (used with a sing. v.) the theoretical and practical application …
128Sundial — A sundial is a device that measures time by the position of the Sun. In common designs such as the horizontal sundial, the sun casts a shadow from its style (a thin rod or a sharp, straight edge) onto a flat surface marked with lines indicating… …
