How to calculate on ground aircraft yaw rate knowing the longitudinal speed and inferred yaw angle Please consider the following scenario: 


a generic aircraft is on-ground taxing at 50 feet per second (~15.25 m/s, ~29.5 knots)
The pilot inferred 20 degrees of yaw


How can I calculate the yaw rate of the aircraft? Do I have enough information to calculate it?
Do I have enough information to calculate it?


No.

Yaw rate is $rad/s$. You have an angle, $rad$ (or degrees), and you have a linear speed, in $m/s$.

You cannot obtain a $rad/s$ value from these two data points.

You need the time interval over which the change in yaw has been observed.