A disk with a rotational inertia of 2.0 kg m2 and a radius of 1.6 m is free to rotate about a frictionless axis perpendicular to the disk's face and passing through its center. A force of 5.0 N is applied tangentially to the rim of the disk. What is the angular acceleration of the disk as a result of this applied force? a) 4.0 rad/s2
b) 1.0 rad/s2
c) 2.0 rad/s2
d) 0.40 rad/s2
e) 0.80 rad/s2

a) 4.0 rad/s2

Explanation:

       τ = I  * α (1)

        where τ is the net external torque applied, I is the rotational inertia

       of  the body with respect to the axis of rotation, and α is the angular

       acceleration caused by the torque.

       where τ = external net torque applied by Fnet, r is the distance    

       between the axis of rotation and the line of Fnet, and θ is the

      angle between both vectors.

      In this particular case, as Fnet  is applied tangentially to the disk, Fnet

     and r are perpendicular each other.

where are the vectors ?