physics question?

Question

A solid cylindrical disk has a radius of 0.17 m. It is mounted to an axle that is perpendicular to the circular end of the disk at its center. When a 45 N force is applied tangentially to the disk, perpendicular to the radius, the disk acquires an angular acceleration of 90 rad/s2. What is the mass of the disk

Answer 1

The moment of inertia is I
I=m*r^2/2 for a disk
also
torque=I*α
45=I*90
I=.5=m*0.17^2/2
1/(0.17^2)=m
34.6 kg
j