PX155 - E1 - circular motion

start with a point mass moving in a circle at a constant speed
definitions:
- centre of rotation: centre of the circle described by the particle
- plane of rotation: the 2D plane in which the circle lies
- axis of rotation: a line through the rotation through the centre of rotation and normal to the plane of rotation
$s = r θ$ , so, speed $v = \frac{d s}{d t} = d \frac{r θ}{d t} = r \frac{d θ}{d t}$
define $ω = \frac{d θ}{d t}$ as the angular speed in $r a d . s^{-} 1$
- $v = ω r$
period is the time for one rotation: $P = \frac{2 π}{ω}$