Browse Definitions :
Definition

radian per second (rad/s or rad/sec)

The radian per second (symbolized rad/s or rad/sec) is the Standard International ( SI ) unit of angular (rotational) speed. This quantity can be defined in either of two senses: average or instantaneous.

Average angular speed is obtained by measuring the angle in radian s through which an object rotates in a certain number of seconds, and then dividing the total angle by the time. If u avg represents the average angular speed of an object (in radians per second) during a time interval t (in seconds), and the angle through which the object rotates in that time is equal to q (in radians), then:

u avg = q / t

Instantaneous angular speed is more difficult to intuit, because it involves an expression of motion over an "infinitely short" interval of time. Let p represent a specific point in time. Suppose an object is in rotational motion at about that time. The average angular speed can be measured over increasingly short time intervals centered at p , for example:

[ p -4, p +4]
[ p -3, p +3]
[ p -2 , p +2]
[ p -1, p +1]
[ p -0.5, p +0.5]
[ p -0.25, p +0.25]
.
.
.
[ p - x , p + x ]
.
.
.

where the added and subtracted numbers represent seconds. The instantaneous angular speed, u inst , is the limit of the measured average speed as x approaches zero. This is a theoretical value, because it cannot be obtained except by inference from measurements made over progressively shorter time spans.

It is important to realize that angular speed is not the same thing as angular velocity. Angular speed is a Scalar (dimensionless) quantity, while angular velocity is a vector quantity consisting of angular speed and direction in the form of a rotational sense (clockwise or counterclockwise). We might say the earth rotates at at 7.272 x 10 -5 rad/s, and this tells us its angular speed. Or we might say the earth rotates at at 0.00007272 (7.272 x 10 -5 ) rad/s counterclockwise relative to the sun as viewed from above the north geographic pole; this tells us the earth's angular velocity. As with angular speed, we might specify either the average angular velocity over a period of time, or the instantaneous angular velocity at an exact moment in time.

In the case of the earth, the instantaneous angular velocity is essentially constant, and it can be said that u inst = u avg . In the case of a moving car or truck, the angular speeds of the wheels, axles, and drive shaft often change, and the statement u inst = u avg is, in general, not true.

Also see radian , second , radian per second squared , and Standard International ( SI ) System of Units.

This was last updated in March 2011
SearchNetworking
  • network packet

    A network packet is a basic unit of data that's grouped together and transferred over a computer network, typically a ...

  • virtual network functions (VNFs)

    Virtual network functions (VNFs) are virtualized tasks formerly carried out by proprietary, dedicated hardware.

  • network functions virtualization (NFV)

    Network functions virtualization (NFV) is a network architecture model designed to virtualize network services that have ...

SearchSecurity
  • What is cybersecurity?

    Cybersecurity is the protection of internet-connected systems such as hardware, software and data from cyberthreats.

  • Android System WebView

    Android System WebView is a system component for the Android operating system (OS) that allows Android apps to display web ...

  • data masking

    Data masking is a method of creating a structurally similar but inauthentic version of an organization's data that can be used ...

SearchCIO
  • privacy compliance

    Privacy compliance is a company's accordance with established personal information protection guidelines, specifications or ...

  • contingent workforce

    A contingent workforce is a labor pool whose members are hired by an organization on an on-demand basis.

  • product development (new product development -- NPD)

    Product development, also called new product management, is a series of steps that includes the conceptualization, design, ...

SearchHRSoftware
  • talent acquisition

    Talent acquisition is the strategic process employers use to analyze their long-term talent needs in the context of business ...

  • employee retention

    Employee retention is the organizational goal of keeping productive and talented workers and reducing turnover by fostering a ...

  • hybrid work model

    A hybrid work model is a workforce structure that includes employees who work remotely and those who work on site, in a company's...

SearchCustomerExperience
  • Salesforce Trailhead

    Salesforce Trailhead is a series of online tutorials that coach beginner and intermediate developers who need to learn how to ...

  • Salesforce

    Salesforce, Inc. is a cloud computing and social enterprise software-as-a-service (SaaS) provider based in San Francisco.

  • data clean room

    A data clean room is a technology service that helps content platforms keep first person user data private when interacting with ...

Close