A thin hoop of radius $R$ and mass $M$ resides in a vertical plane. A point mass $m$ is fixed to the inner perimeter of the hoop. This system is placed onto a horizontal, initially stationary conveyor belt in its stable equilibrium position so that the plane of the hoop is parallel with the sides of the belt. In a given moment the conveyor belt starts to move with constant acceleration $a$.

A1 At least what should the value of $a$ be if the point mass passes through its topmost position?

A2 Find the maximal angular speed of the hoop in the case when the acceleration of the conveyor belt is slightly smaller than the value calculated in the previous subquestion.

The hoop does not slip on the conveyor belt. The plane of the hoop remains vertical, so the motion can be considered two-dimensional.