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Inverse second

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(Redirected from Reciprocal second)
inverse second
Unit systemSI
Unit offrequency
1 s-1 in ...... is equal to ...
   SI units   Hz

The inverse second or reciprocal second (s−1), also called per second, is a unit defined as the multiplicative inverse of the second (a unit of time). It is applicable for physical quantities of dimension reciprocal time, such as frequency and strain rate.

It is dimensionally equivalent to:

However, the special names and symbols above for s−1 are recommend for clarity.[a][b]

Reciprocal second should not be confused with radian per second (rad⋅s−1), the SI unit for angular frequency and angular velocity. As the radian is a dimensionless unit, radian per second is dimensionally consistent with reciprocal second. However, they are used for different kinds of quantity, frequency and angular frequency, whose numerical value differs by 2π.

The inverse minute or reciprocal minute (min−1), also called per minute, is 60−1 s−1, as 1 min = 60 s; it is used in quantities of type "counts per minute", such as:

Inverse square second (s-2) is involved in the units of linear acceleration, angular acceleration, and rotational acceleration.

See also



  1. ^ "The SI unit of frequency is given as the hertz, implying the unit cycles per second; the SI unit of angular velocity is given as the radian per second; and the SI unit of activity is designated the becquerel, implying the unit counts per second. Although it would be formally correct to write all three of these units as the reciprocal second, the use of the different names emphasises the different nature of the quantities concerned."[1]
  2. ^ "(d) The hertz is used only for periodic phenomena, and the becquerel (Bq) is used only for stochastic processes in activity referred to a radionuclide."[2]


  1. ^ "Units with special names and symbols; units that incorporate special names and symbols".
  2. ^ "BIPM - Table 3". BIPM. Retrieved 2012-10-24.