Change in the velocity of a body with respect to time. Since velocity is a vector quantity, involving both magnitude and direction, acceleration is also a vector. In order to produce an acceleration, a force must be applied to the body.

In physics, number of periodic oscillations, vibrations, or waves occurring per unit of time. The SI unit of frequency is the hertz (Hz), one hertz being equivalent to one cycle per second.

Force of attraction that arises between objects by virtue of their masses. The larger the mass of an object the more strongly it attracts other objects.

Branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this name at a few universities.

From Collins Dictionary of Astronomy
Symbol: vr. The velocity of a star along the line of sight of an observer. It is calculated directly from the doppler shift (see Doppler effect) in the lines of the star's spectrum: if the star is receding there will be a redshift in its spectral lines and the radial velocity will be positive; an approaching star will produce a blueshift and the velocity will be negative.

Longitudinal wave motion with which sound energy travels through a medium. It carries energy away from the source of the sound without carrying the material itself with it.

Physical principle, enunciated by Werner Heisenberg in 1927, that places an absolute, theoretical limit on the combined accuracy of certain pairs of simultaneous, related measurements. The accuracy of a measurement is given by the uncertainty in the result; if the measurement is exact, the uncertainty is zero.

From The Penguin Dictionary of Mathematics
Symbol: v. The rate of change of position with time when the direction of motion is specified. Velocity v is thus a vector quantity; its magnitude v is referred to as speed.

Compute pretty much anything computable.

One of THE authoritative sources for such data

List of free databases of Standard Reference Data

Key information about the chemical elements in the periodic table.

Refractive index database of many materials.