A 25 × 50 mm bar of rectangular cross-section is made of plain carbon steel 40C8 \left(S_{y t}=380 N / mm ^{2} \text { and } E=207000 N / mm ^{2}\right) . The length of the bar is 500 mm. The two ends of the bar are hinged and the factor of safety is 2.5. The bar is subjected to axial compressive force.
(i) Determine the slenderness ratio;
(ii) Which of the two equations—Euler’s or Johnson’s—will you apply to the bar?
(iii) What is the safe compressive force for the bar?