Q: Types of circular acceleration? To my knowledge there are three types of acceleration when a body (e.g. a rod) is moving in a circle about an axis. These are:


*

*Angular acceleration : this is the rate of change of angular velocity.

*Tangential acceleration : this is the linear acceleration of the system in a tangential direction to the circle and equals the radius times the angular acceleration.

*Radial/centripetal acceleration : this is the linear acceleration of the system that is directed inwards towards the center of the circle.
I also think there are two types of velocity:


*

*Linear velocity: this is its velocity in the tangential direction and is constantly changing

*Angular velocity or angular frequency: this is the rate of change of angle.
Is the above correct? And have I missed anything? 

A: No it's not correct, or at least it's headed in the wrong direction.  Properly, you define acceleration, in either 2 or 3 dimensions as fits your situation, by means of vector coefficients.  You can use Cartesian (x and y) systems or you can use Polar (radius and angle) systems, and report/calculate the acceleration components for each vector component.)
In 3D, those expand to (x,y,z) cartesian,  (rho, theta, phi (polar angle) in spherical polar coordinates, and a couple other possibilities as well.

A: No. Frequency is defined as 2π*θ/t where theta is the angle rotated for a time t. You maybe tempted to equate frequency to angular velocity. But it is not so. Angular velocity = dθ/dt. Angular frequency= 2*pi*(Integral of x over time interval t)/t
