Plan the Solution  
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The figure shows an L shaped rigid bar A B C D with a horizontal segment A B C of length 750 millimeters and a vertical segment C D of height 300 millimeters. The bar is pinned at C and supported by vertical and horizontal rods labeled 1 and 2 of length 600 millimeters and 150 millimeters at A and D respectively. The other end of the support rods is pinned. A load P which equals 80 kilo newtons directed vertically downwards acts at the point B which is 400 millimeters to the right of C. The bar is deflected downwards at the point A and deflected leftwards at the point D.

Bar ABCD is assumed to be rigid, meaning that it does not bend when load P is applied. Since it is pinned, bar ABCD cannot translate; however, it can rotate about C. As it rotates, points A and D move downward and to the left, respectively.

This movement causes elongation in aluminum rod (1) and contraction in brass rod (2). Rods (1) and (2) resist this deformation, developing internal forces and internal normal stresses.