A computer disk drive is turned on starting from rest and has a constant angular acceleration. If it took 0.750 seconds for the drive to make its second revolution,
1. How long did it take to make the first complete revolution?
2. What is its angular acceleration in rad/s2?
Answer:
a) Θ = ω₀*t + ½αt² To complete first revolution 2π rads = 0*t + ½αt² and to complete the first and second combined 4π rads = 0*t + ½α(t+0.810s)² Divide second by first: 2 = (t + 0.810s)² / t² This is quadratic in t and has roots at t = -0.336 s ← ignore and t = 1.96 s
b) Use either equation from above: 2π rads = 0*t + ½α(1.96s)² α = 3.27 rad/s²