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abstraction > mathematical concept > number > quantity

quantity
subject			fact

quantity	has unit
	has definition A number with specific units
	is a kind of number
number	has value

Kinds of quantity :

• angle (48 kinds, 158 facts)
• angular momentum (4 facts) (L) - The angular momentum of a system about a specified origin is the sum over all the particles in the system (or an integral over the different elements of the system if it is continuous) of the vector products of the radius vector joining each particle to the origin and the momentum of the particle. For a closed system it is conserved by virtue of the isotropy of space., The product of mass and angular velocity for an object in rotation; similar to linear momentum. In quantum mechanics, angular momentum is quantized, i.e., is measured in indivisible units equivalent to Planck's constant divided by 2 pi. This corresponds classically to only certain frequencies of rotation being allowed.
• area (1 kind, 7 facts)
• coordinate component (19 kinds, 68 facts) - A component of a coordinate system, components are usually an angle or a length
• density (3 kinds, 13 facts) - The amount per unit volume, The mean density of a celestial body is generally reckoned as its mass divided by its volume, expressed either in comparison with the density of water, in kilograms per cubic meter, or in relation to some other known density. The mean density of the Earth is thus 5.5 times that of water, i.e. 5.5 × 10³ kg m^-3 and is just less than four times that of the Sun. Yet the mean density of rocks at the surface is about half the overall mean value, and that of the Earth's central core is perhaps 2 1/2 times the overall value., An object's mass divided by its volume. Cotton has a low density; lead has a high density. Red giants have a low density; white dwarfs have a high density.
• electromagnetic quantity (15 kinds, 54 facts)
• energy (19 kinds, 49 facts)
• equatorial sky area (99 kinds, 633 facts) - A fixed region on the sky defined using equatorial coordinates
• force quantity (1 kind, 5 facts) - Agency responsible for a change in a system. In Newtonian mechanics, gravitational force bends the moon away from the straight trajectory it would otherwise pursue.
• frequency (5 kinds, 19 facts) (ν) - The number of peaks (often called crests) of a propagating wave that cross a given point in a unit of time. For example, if 1000 peaks cross a given point in one second, one says that the frequency is 1000 cycles per second or 1000 hertz., The number of complete wave cycles a wave completes each second., The number of oscillations or wave cycles per second passing a given point. For electromagnetic radiation, the product of the frequency and the wavelength is the speed of light., The number of cycles or complete alternations per unit time of a carrier wave, band, or oscillation., Number of oscillations per second of an electromagnetic wave. The amplitude of a wave depends on the intensity; the wavelength, on the frequency.
• length (22 kinds, 99 facts)
• mass (18 kinds, 82 facts) - The quantitative property of an object due to the matter it contains. (Weight, in contrast, describes a force with which a body is attracted towards a gravitational focus.) Units of mass are grams and kilograms., Measure of the amount of matter in an object. Inertial mass indicates the object's resistance to changes in its state of motion. Gravitational mass indicates its response to the gravitational force. In the general theory of relativity, gravitational and inertial mass are revealed to be aspects of the same quantity., The measure of the inertia of an object, determined by observing the acceleration when a known force is applied. The gravitational force acting on an object is found to be proportional to its mass, as is the gravitational force that it exerts on other objects.
• orbital quantity (11 kinds, 52 facts) - A quantity used for calculating orbits
• power
• pressure (5 kinds, 14 facts) - The force exerted over a surface divided by its area.
• quantum quantity (7 kinds, 32 facts)
• radiation measurement (106 kinds, 342 facts)
• solid angle (1 kind, 4 facts) - A measure of the angular size of an extended object, equal to the area it subtends on the surface of a sphere of unit radius.
• statistical quantity (7 kinds, 20 facts)
• temperature (7 kinds, 18 facts) - A measure of the average kinetic energy of the particles of a system.
• time (16 kinds, 62 facts) - A dimension distinguishing past, present, and future. In relativity, time is portrayed as a geometrical dimension, analogous to the dimensions of space.
• velocity (20 kinds, 50 facts) - The speed and the direction of an object's motion.