A figure skater begins spinning counterclockwise at an angular speed of 4.2 π rad/s. During a 4.5 s interval, she slowly pulls her arms

Question

inward and finally spins at 7.7 π rad/s.
What is her average angular acceleration
during this time interval?
Answer in units of rad/s^2

Answer 1

acceleration = change in speed / change in time
= (7.7 - 4.2) pi / 4.5 rad/s^2

Answer 2

V = Vo + a*T.
7.7pi = 4.2pi + a*4.5,
4.5a = 7.7pi-4.2pi = 3.5pi,
a = 2.44 rad/s^2.