Angular frequency

 ( Angle ) 

In physics, angular frequency (symbol ω), also called angular speed and angular rate, is a scalar measure of the angle rate (the angle per unit time) or the temporal rate of change of the phase argument of a sinusoidal waveform or sine function (for example, in oscillations and waves). Angular frequency (or angular speed) is the magnitude of the pseudovector quantity angular velocity.

(UP1)

Angular frequency can be obtained by multiplying rotational frequency, ν (or ordinary frequency, f) by a full turn (2 radians): . It can also be formulated as , the instantaneous rate of change of the angular displacement, θ, with respect to time,  t. [1] (11 pages)

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Unit In SI units, angular frequency is normally presented in the unit radian per second. The unit hertz (Hz) is dimensionally equivalent, but by convention it is only used for frequency  f, never for angular frequency  ω. This convention is used to help avoid the confusion

Lawrence S. Lerner (1996). 9780867204797, Jones & Bartlett Learning. . ISBN 9780867204797

that arises when dealing with quantities such as frequency and angular quantities because the units of measure (such as cycle or radian) are considered to be one and hence may be omitted when expressing quantities in terms of SI units.

In digital signal processing, the frequency may be normalized by the sampling rate, yielding the normalized frequency.

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Examples

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Circular motion In a rotating or orbiting object, there is a relation between distance from the axis, $r$, tangential speed, $v$, and the angular frequency of the rotation. During one period, $T$, a body in circular motion travels a distance $vT$. This distance is also equal to the circumference of the path traced out by the body, $2\backslash pi\; r$. Setting these two quantities equal, and recalling the link between period and angular frequency we obtain: $\backslash omega\; =\; v/r.$ Circular motion on the unit circle is given by $$\backslash omega\; =\; \backslash frac\{2\; \backslash pi\}\{T\}\; =\; \{2\; \backslash pi\; f\}\; ,$$ where:

• ω is the angular frequency (SI unit: radians per second),
• T is the Frequency (SI unit: ),
• f is the ordinary frequency (SI unit: hertz).

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Oscillations of a spring An object attached to a spring can Oscillation. If the spring is assumed to be ideal and massless with no damping, then the motion is simple and harmonic with an angular frequency given by

Raymond A. Serway (2026). 9780534464790, Brooks / Cole – Thomson Learning. . ISBN 9780534464790

$$\backslash omega\; =\; \backslash sqrt\{\backslash frac\{k\}\{m\}\},$$ where

• k is the spring constant,
• m is the mass of the object.

ω is referred to as the natural angular frequency (sometimes be denoted as ω₀).

As the object oscillates, its acceleration can be calculated by $$a\; =\; -\backslash omega^2\; x,$$ where x is displacement from an equilibrium position.

Using standard frequency f, this equation would be $$a\; =\; -(2\; \backslash pi\; f)^2\; x.$$

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LC circuits The resonant angular frequency in a series LC circuit equals the square root of the reciprocal of the product of the capacitance ( C, with SI unit farad) and the inductance of the circuit ( L, with SI unit henry):

Mahmood Nahvi (2026). 9780071393072, McGraw-Hill Companies (McGraw-Hill Professional). . ISBN 9780071393072

(LC1) $$\backslash omega\; =\; \backslash sqrt\{\backslash frac\{1\}\{LC\}\}.$$

Adding series resistance (for example, due to the resistance of the wire in a coil) does not change the resonant frequency of the series LC circuit. For a parallel tuned circuit, the above equation is often a useful approximation, but the resonant frequency does depend on the losses of parallel elements.

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Terminology Although angular frequency is often loosely referred to as frequency, it differs from frequency by a factor of 2, which potentially leads confusion when the distinction is not made clear.

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See also

• Cycle per second
• Radian per second
• Degree (angle)
• Mean motion
• Rotational frequency
• Simple harmonic motion

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References and notes Related Reading:

• Richard P. Olenick (2026). 9780521715928, Cambridge University Press. . ISBN 9780521715928

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