When talking about circular motion, you may need to use RADIANS to express angles. The angle in radians is defined as arc length divided by the radius of the circle. To convert from degrees to radians: **angle in radians (θ) = (2pi/360) x angle in degrees**

The ANGULAR SPEED is the angle an object rotates through per second: **ω = θ/t**

you can link linear speed (distance/time) with angular speed: **v=ωr**

Circular motion has a **frequency** and **period**: ω = 2**πf and T = 2****π /** ω** **

Objects travelling in circles are acclerating because their veolcity is constantly changing (because their direction is constantly changing.) This is called CENTRIPETAL ACCELERATION - it is always directed towards the **center of the circle**. It can be calculated using these equations: b **a = v² / r ** and **a = rω²**

By Newtons Second Law, acceleration must be cause by a force. Centripetal acceleration must be caused by a CENTRIPETAL FORCE this is **not** an extra force - it is just used to describe the force is ** F = mv²/r ** **a = rω²** causing the centripetal acceleration - it could be tension etc.

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