$B$ Bar $AB$ is rigid. At end $B,$ there is a mass $m$ at end $B.$ The stiffness of the support at end $B$

is k $.$

$2\mathrm{.}1)$ Neglect the mass of the rigid bar, determine the natural frequency of the system.

$2\mathrm{.}2)$ The mass of the rigid bar is not negligible. The mass of the bar distribute over the

lenth evenly. The mass per unit lenth is $\frac{?}{\text{b}\text{a}\text{r}}(m).$

Determine the natural frequency of the system$($ accurately, not aproximately$).$