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abstraction > mathematical concept > number > quantity > velocity

velocity
subject			fact

velocity	has base unit length per unit time
	has definition The speed and the direction of an object's motion.
	is a kind of quantity
quantity	has unit
number	has value

Kinds of velocity :

• equatorial velocity (1 kind, 4 facts) - The velocity at the surface of a rotating body, on its equator
• escape velocity (4 facts) - Speed a satellite must attain in order to free itself from returning to the parent body under the effects of gravity., The speed at which an object can leave another object behind, without being recalled by its gravitational force. The escape velocity of Earth - which must, for instance, be attained by a spacecraft if it is to reach another planet - is 25,000 miles per hour., The velocity that a body requires to achieve a parabolic orbit around its primary (V_e = sqrt(2GM/R)). Escape velocity at Earth's surface is 11.2 km s^-1; of Moon, 2.4 km s^-1; of Sun, 617.7 km s^-1 (cf. orbital velocity).
• galactic velocity component (5 kinds, 12 facts) - One of three components of a star's motion with respect to the center of a galaxy.
• galaxy peculiar velocity (2 facts) - A deviation in the velocity of a galaxy from that expected on the basis of a uniform expansion of the universe. (See Hubble law.)
• orbital velocity (2 facts) - Velocity required by a body to achieve a circular orbit around its primary: V_orb = (GM / r)^1/2.
• peculiar velocity (5 kinds, 15 facts) - Velocity with respect to the Local Standard of Rest.
• radial velocity (3 facts) - Velocity along the line of sight toward (-) or away from (+) the observer., The speed at which an object moves toward or away from us. It can be measured from a star's spectrum: a star moving toward us has a blueshifted spectrum, and a star moving away from us has a redshifted spectrum. The larger the blueshift or redshift, the larger the radial velocity. The present radial-velocity champion is a star in the constellation Lacerta named Giclas 233-27, which moves toward us at 583 kilometers per second.
• space motion (2 facts) - Velocity of a star with respect to the Sun; hypotenuse of the right triangle formed by its radial and tangential velocities (cf. peculiar velocity). Space motion vectors are U (in the direction of the galactic anticenter), V (in the direction of galactic rotation), and W (in the direction of the galactic north pole).
• tangential velocity (3 facts) (transverse velocity) - A star's velocity across an observer's line of sight. To calculate a star's tangential velocity, one must know the star's distance and proper motion.