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Part 3: Space and Time

Length, area, volume, angle, time

42 entries· Edition 2019FR→ About this part

3-1length

l

L

m

·metre

linear extent in space between any two points

3-1.2

width, breadth

b

B

m

·metre

minimum length of a straight line segment between two parallel straight lines (in two dimensions) or planes (in three dimensions) that…

3-1.3

height, depth, altitude

h

H

m

·metre

minimum length of a straight line segment between a point and a reference line or reference surface

3-1.4

thickness

d

δ

m

d

D

m

·metre

width (t3-1.2) of a circle, cylinder or sphere

3-1.6

radius

r

R

m

·metre

half of a diameter (t3-1.5)

3-1.7

path length, arc length

s

m

·metre

length of a rectifiable curve between two of its points

3-1.8

distance

d

r

m

·metre

shortest path length (t3-1.7) between two points in a metric space

3-1.9

radial distance

r_{Q}

ρ

m

·metre

distance (t3-1.8), where one point is located on an axis or within a closed non self-intersecting curve or surface

3-1.10

position vector

r

m

·metre

vector (iso80000-2) quantity from the origin of a coordinate system to a point in space

3-1.11

displacement

Δ r

m

·metre

vector (iso80000-2) quantity between any two points in space

3-1.12

radius of curvature

ρ

m

·metre

radius (t3-1.6) of the osculating circle of a planar curve at a particular point of the curve

3-2curvature

3-2

curvature

κ

m^{- 1}

·per metre

inverse of the radius of curvature (t3-1.12)

3-3area, area

3-3

area, area

A

S

m^{2}

·square metre

extent of a two-dimensional geometrical shape

3-4volume

3-4

volume

V

(S)

m^{3}

·cubic metre

extent of a three-dimensional geometrical shape

3-5angular measure, angular measure

3-5

angular measure, angular measure

α

β

γ

r a d

1

·radian, one

measure of a geometric figure, called plane angle, formed by two rays, called the sides of the plane angle, emanating from a common point,…

3-6rotational displacement, angular displacement

3-6

rotational displacement, angular displacement

ϑ

ϕ

r a d

1

·radian, one

quotient of the traversed circular path length (t3-1.7) of a point in space during a rotation and its distance (t3-1.8) from the axis or…

3-7phase angle

3-7

phase angle

φ

ϕ

r a d

1

·radian, one

angular measure (t3-5) between the positive real axis and the radius of the polar representation of the complex number in the complex plane

3-8solid angular measure

3-8

solid angular measure

Ω

s r

1

·steradian, one

measure of a conical geometric figure, called solid angle, formed by all rays, originating from a common point, called the vertex of the…

3-9duration

3-9

duration

t

s

·second

measure of the time difference between two events

3-10velocity

3-10.1

velocity

v

(v)

u, v, w

(u, v, w)

m \cdot s^{-} 1

·metre per second

vector (iso80000-2) quantity giving the rate of change of a position vector (t3-1.10)

3-10.2

speed

v

(v)

m \cdot s^{-} 1

·metre per second

magnitude (iso80000-2) of the velocity (t3-10.1)

3-11acceleration

3-11

acceleration

a

m \cdot s^{-} 2

·metre per second squared

vector (iso80000-2) quantity giving the rate of change of velocity (t3-10.1)

3-12angular velocity

3-12

angular velocity

ω

r a d \cdot s^{- 1}

s^{- 1}

·radian per second, per second

vector (iso80000-2) quantity giving the rate of change of the rotational displacement (t3-6) as its magnitude (iso80000-2) and with a…

3-13angular acceleration

3-13

angular acceleration

α

r a d \cdot s^{- 2}

s^{- 2}

·radian per second squared, per second squared

vector (iso80000-2) quantity giving the rate of change of angular velocity (t3-12)

3-14period duration, period

3-14

period duration, period

T

s

·second

duration (t3-9) of one cycle of a periodic event

3-15time constant

3-15

time constant

τ

T

s

·second

parameter characterizing the response to a step input of a first-order, linear time-invariant system

3-16rotation

3-16

rotation

N

1

·one

number of revolutions

3-17frequency

3-17.1

frequency

f

ν

H z

s^{- 1}

·hertz, per second

inverse of period duration (t3-14)

3-17.2

rotational frequency

n

s^{- 1}

·per second

rate of change of rotation (t3-16)

3-18angular frequency, angular frequency

3-18

angular frequency, angular frequency

ω

r a d \cdot s^{- 1}

s^{- 1}

·radian per second, per second

rate of change of the phase angle (t3-7)

3-19wavelength

3-19

wavelength

λ

m

·metre

length (t3-1.1) of the repetition interval of a wave

3-20repetency, wavenumber

3-20

repetency, wavenumber

σ

\tilde{v}

m^{- 1}

·per metre

inverse of the wavelength (t3-19)

3-21wave vector

3-21

wave vector

k

m^{- 1}

·per metre

vector normal to the surfaces of constant phase angle (t3-7) of a wave, with the magnitude (iso80000-2) of repetency (t3-20)

3-22angular repetency, angular wavenumber

3-22

angular repetency, angular wavenumber

k

m^{- 1}

·per metre

magnitude (iso80000-2) of the wave vector (t3-21)

3-23phase velocity, phase speed

3-23.1

phase velocity, phase speed

c, v, (v)

c_{φ}, v_{φ}, (v_{φ})

m \cdot s^{-} 1

·metre per second

speed with which the phase angle (t3-7) of a wave propagates in space

3-23.2

group velocity, group speed

c_{g}, v_{g}, (v_{g})

m \cdot s^{-} 1

·metre per second

speed with which the envelope of a wave propagates in space

3-24damping coefficient

3-24

damping coefficient

δ

s^{-} 1

·per second

inverse of the time constant (t3-15) of an exponentially varying quantity

3-25logarithmic decrement

3-25

logarithmic decrement

Λ

1

·one

product of damping coefficient (t3-24) and period duration (t3-14)

3-26attenuation, extinction

3-26.1

attenuation, extinction

α

m^{- 1}

·per metre

gradual decrease in magnitude (iso80000-2) of any kind of flux through a medium

3-26.2

phase coefficient

β

r a d \cdot m^{- 1}

m^{- 1}

·radian per metre, per metre

change of phase angle (t3-7) with the length (t3-1.1) along the path travelled by a plane wave

3-26.3

propagation coefficient

γ

m^{- 1}

·per metre

measure of the change of amplitude and phase angle (t3-7) of a plane wave propagating in a given direction

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