Beam stands on one support. Support is unmovable and it's placed directly in its middle. Beam is fixed to the ceiling and to the ground by roda. Rods are fixed to the beam in its specific points. External force P works at the end of beam. Hooke's law will be applied to calculate stress in beam. Equilibrium equations for forces and torques will be written. Minumum beam's cross-sectional area A has to calculated to provide enough strength for beam.