ANGULAR MEASUREMENT
Angle θ : Orientation of an object relative to some fixed axis.

• The angle θ measures the state of rotation of an object at a given moment.
• For a rotating object, θ will change with time.

Unit Comparison:

Units	A circle divided into
Degrees:	360 equally spaced units.
Radians:	2π equally spaced units.
Grads:	400 equally spaced units.

Degrees (o)	SI: Radians (rad)	Grads
1 rev = 360o	1 rev = 2π rad	1 rev = 400 grads

• The unit "radian" is not really a true unit. It is a marker that specifies how a circle will be divided up. Often you will need to drop "rad" in equations that relate linear and rotational quantities, such as s = r θ. Otherwise, you would have that "m = m ^. rad" which is impossible if "rad" stood for a unit.