To solve this problem it is only necessary to apply the kinematic equations of angular motion description, for this purpose we know by definition that,

Where,
Angular Displacement
Angular Acceleration
Angular velocity
Initial angular displacement
For this case we have neither angular velocity nor initial angular displacement, then

Re-arrange for 

Replacing our values,


Therefore the ANgular acceleration of the mass is 
Answer:
Explained
Explanation:
following are characteristics of scientific thinking and investigating
1. Critical thinking
2. A curious mind
3. Possessing a Skeptical attitude
4. Problem solving attitude
5.A obervant of empirical evidences
A scientific theory is a unifying and self-consistent explanation of fundamental natural processes or phenomena that is totally constructed of corroborated hypotheses
It is an example of rolling friction because balls roll.
Answer is ROLLING