Meriam, Kraige & Bolton — Introduction to Three-Dimensional Dynamics of Rigid Bodies: Problem 7_84

7/84 If the homogeneous triangular plate of Prob. 7/83 is released from rest in the position shown, determine the magnitude of the bearing reaction at \(A\) after the plate has rotated 90°. [Context from 7/83: The homogeneous thin triangular plate of mass \(m\) is welded to the horizontal shaft, which rotates freely in the bearings at \(A\) and \(B\). The plate is released from a horizontal position. Dimensions: bearing \(A\) is at distance \(a\) from the start of the plate base \(b\); bearing \(B\) is at distance \(a\) from the end of the plate base; the height of the triangle is \(a\) and its vertex is centered over the base.]