Rigid Plate Deflection at D  
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The figure shows a rigid triangular plate B C D which is pinned at C, supported at B by a horizontal rod of length 1200 millimeters and supported at D by a vertical post of height 600 millimeters. The clearance between the post and the plate is 1.5 millimeters. The post is fixed to the ground at E and the rod is fixed to a wall at A. The plate has dimensions 600 millimeters along C D and 480 millimeters along B C. A load P directed vertically downwards acts on the plate.

From the statement of the problem, it is known that the load P produces a normal strain of -1,800 με in post (2). Since the strain is negative, the post must contract.

How must the rigid plate move to cause contraction in the post?