In an assembly which we will expand upon in the torsion section, two rods are attached lengthwise via a plate P, shown as transparent in the image for clarity. The bottom rod is thicker (radius = 18 mm) than the top rod (radius = 10 mm), but they are of equal length (750 mm). The top rod is pulled (upwards) axially with a force of 15 kN, while at the same time the bottom rod is pushed (downwards) axially via the plate with an unknown force F. If the uppermost point of the top rod does not move, calculate the unknown force applied to plate P as well as the stresses developed in both members. Assume that both rods are made of the same material, with E = 50 GPa. Report your stresses as positive for tension and negative for compression. [Adapted from Philpot] |F| (kN) = otop (MPa) = bottom (MPa) =