Q$\mathrm{.}3($a$)$ What do you understand by buckling of a column? Derive an expression for Euler Buckling load $(P_{cr}).$

Q$\mathrm{.}3($b$)$ A cantilever beam of length $L$ is acted upon by a point load at a distance of $\frac{L}{2}$ from the fixed end. Find the deflection at the free end. Take EI as a constant.