I realized that I should have used 0.25m as the height, not π/2 radians. As for the rest of the problem, I needed to include KT. After fixing this I finally got the correct answer of 1.87 m/s.
I am also working on this problem. I've been using conservation of energy and set up the equation:
mgh = ½(2/5mr2)(ω2)
The sphere rotates 90o (based on the diagram we have) and I converted that to (π/2) radians and used that as my height.
After plugging in values for variables I got:
5.393...