A disk of radius 10 cm speeds up from rest. It turns 60 radians reaching an angular velocity of 15 rad/s. What was the angular acceleration? B.How long did it take the disk to reach this velocity?
Is this correct
A=wf^2-w0^2/2×delta(theta)
A=15^2-0^2/2(60)
A=15^2/2(60)
A=1.875 rad/s^2
T=wf-w0/a
T=15-0/1.875
T=8s
omega = alpha * t if omega is 0 at t = 0 andalpha is constant
so
15 = alpha * t
so t = 15/alpha
theta = (1/2) alpha t^2
60 = (1/2) alpha (225/alpha^2)
or
120 alpha = 225
alpha = 1.875 radians/ second^2 { We agree}
t = 15 /1.875 = 8 seconds {We agree }