A ceiling fan is rotating anticlockwise at

PHYSICS · Subjective · AP · Physics 1: Algebra-based · Torque and Rotational Dynamics · Torque and Rotational Dynamics

Problem

20\,\text{rad}\,\text{s}^{-1}

. After the switch is turned off, it comes to rest in

4\,\text{s}

with uniform angular deceleration. Calculate the angular acceleration and state its sign as per the usual convention.