The truss shown in the figure has four members of length $\text{l}$ and flexural rigidity $\text{EI}$, and one member of length $l\sqrt{2}$ and flexural rigidity $\text{4EI}$. The truss is loaded by a pair of forces of magnitude $\text{P}$, as shown in the figure.
The smallest value of $\text{P}$, at which any of the truss members will buckle is
- $\dfrac{\sqrt{2}\pi ^{2}EI}{l^{2}} \\$
- $\dfrac{\pi ^{2}EI}{l^{2}} \\$
- $\dfrac{2\pi ^{2}EI}{l^{2}} \\$
- $\dfrac{\pi ^{2}EI}{2l^{2}}$