Suppose a revolving door at the bamk is spinning around once every 5 seconds. As you walk through, you push on the door for 2 seconds, which increases the rotational speed so that it rotates once a second. What was the rotational acceleration due to your push?

Answer 1

T = 5 so f = 1/5 and 2 pi f = (2/5)pi rad/s

new T = 1 so f = 1 and 2 pi f = 2 pi rad/s

change in angular velocity =2 pi(4/5)
change in angular velocity per second = angular acceleration = 2 pi (4/5)/2

= 4 pi/5 rad/s^2