Let us assume that the rectangular board shown has a torque T at its centre of mass, due to which it is undergoing angular acceleration in clockwise direction. Let d be the distance from the centre of mass to the edge.
It seems difficult to calculate the force experienced by the ball kept at the edge of the board as a variety of distributions of forces are possible for the same moment. For example, the forces acting on the bottom balls, in i and ii can be calculated to be different: T/d in (i), and T/2d in (ii). (The second case could be considered as a moment with T/2d as the force acting on the bottom and the top balls.)
And there seems to be no reason why a ball kept at the same position can experience different forces depending on whether something has been kept at other position.
Please clarify as to how to proceed to find the forces.