Assuming small oscillation in a free vibration of the pendulum as shown in figure. Determine the natural frequency of this system. Assume the rod is massless.
1
\(\sqrt {\frac{{kl + mg}}{{ml}}} \)
2
\(\sqrt {\frac{{kl + mg}}{{m{l^2}}}} \)
3
\(\sqrt {\frac{{kl + mg}}{m}} \)
4
\(\sqrt {\frac{k}{{ml}}} \)