Solution of task 15.6.1 from the collection of Kepe OE

Solution of task 15.6.1 from the collection of Kepe OE

15.6.1
A homogeneous disk with a radius of 0.4 m can rotate about a horizontal axis,
Perpendicular to the plane of the disk and passing through the point of its rim. What initial
Angular velocity must be reported to the disk, so that it turns a quarter turn?
(Answer 5.72)