Help with the non uniform circular motion ?

[tsherpa]

I am given the moment of inertia of the system ( a fan) and the question asks for me to find the angular acceleration "after the fan is turned on, it takes t = 3.6 s and a total of 12 revolutions to accelerate up to its full speed" ? How I went about solving is that.. I simply converted the rev / sec into rad/ sec (20.94rads/sec). And used this as a final angular velocity, 0 as the initial velocity and the time (3.6) to calculate the acceleration, but I don't get the right answer and I don't know why ?

thanks

 

[edgepflow]

I would apply the following:

θ = θ_{o} + \omega_{o}t + \frac{1}{2}\alphat^{2}

Your physics book should discuss this.

Let me know it it works!