Physics, asked by mansoormansoori302, 4 months ago

physical quantity .... changes rotational axis changes

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Answered by Anonymous
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Answer:

A physical quantity is a property of a material or system that can be quantified ...

Answered by yashodhathanigai
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                                                 Physical Changes

A physical quantity is a property of a material or system that can be quantified by measurement. A physical quantity can be expressed as the combination of a numerical value and a unit. For example, the physical quantity mass can be quantified as n kg, where n is the numerical value and kg is the unit. A physical quantity possesses at least two characteristics in common, one is numerical magnitude and other is the unit in which it is measured.

Subscripts and indices

Subscripts are used for two reasons, to simply attach a name to the quantity or associate it with another quantity, or represent a specific vector, matrix, or tensor component.[clarification needed]

Indices: The use of indices is for mathematical formalism using index notation.

Scalars

A scalar is a physical quantity that has magnitude but no direction. Symbols for physical quantities are usually chosen to be a single letter of the Latin or Greek alphabet, and are printed in italic type.

Vectors

Vectors are physical quantities that possess both magnitude and direction. Symbols for physical quantities that are vectors are in bold type, underlined or with an arrow above. For example, if u is the speed of a particle, then the straightforward notations for its velocity are u, u, or {\displaystyle {\vec {u}}\,\!}\vec{u}\,\!.

Numbers and elementary functions

Numerical quantities, even those denoted by letters, are usually printed in roman (upright) type, though sometimes in italic. Symbols for elementary functions (circular trigonometric, hyperbolic, logarithmic etc.), changes in a quantity like Δ in Δy or operators like d in dx, are also recommended to be printed in roman type.

Units and dimensions

Units

Main article: Units of measurement

There is often a choice of unit, though SI units (including submultiples and multiples of the basic unit) are usually used in scientific contexts due to their ease of use, international familiarity and prescription. For example, a quantity of mass might be represented by the symbol m, and could be expressed in the units kilograms (kg), pounds (lb), or daltons (Da).

Dimensions

Main article: Dimension (physics)

The notion of dimension of a physical quantity was introduced by Joseph Fourier in 1822.[1] By convention, physical quantities are organized in a dimensional system built upon base quantities, each of which is regarded as having its own dimension.

International System of Quantities base quantities

Quantity SI unit Dimension

symbol

Name(s) (Common) symbol(s) Name Symbol

Length, width, height, depth, distance a, b, c, d, h, l, r, s, w, x, y, z metre m L

Time t, τ second s T

Mass m kilogram kg M

Absolute temperature T, θ kelvin K Θ

Amount of substance n mole mol N

Electric current i, I ampere A I

Luminous intensity Iv candela cd J

Plane angle α, β, γ, θ, φ, χ radian rad None

Solid angle ω, Ω steradian sr None

General derived quantities

Derived quantities are those whose definitions are based on other physical quantities (base quantities).

Quantity SI unit Dimensions

Description Symbols

(Spatial) position (vector) r, R, a, d m L

Angular position, angle of rotation (can be treated as vector or scalar) θ, θ rad None

Area, cross-section A, S, Ω m2 L2

Volume τ, V m3 L3

Densities, flows, gradients, and moments

Important and convenient derived quantities such as densities, fluxes, flows, currents are associated with many quantities. Sometimes different terms such as current density and flux density, rate, frequency and current, are used interchangeably in the same context, sometimes they are used uniqueley.  

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