$3.2.2.$ A fixed weight suspended on a spring stretches it in the equilibrium position by a length $\Delta l$. What is the period of vertical oscillations of the load?
Period of oscillation of a spring pendulum $$ T=2\pi\sqrt{\frac{m}{k}} $$ Elastic force, restoring force: $$ F=-k\Delta l=mg\Rightarrow k=\frac{mg}{\Delta l} $$ The period of oscillation of a spring pendulum, being in the equilibrium position, is $\Delta l$ $$ \boxed{T=2\pi\sqrt{\frac{m\Delta l}{mg}}=2\pi\sqrt{\frac{\Delta l}{g}}} $$
$$T=2\pi\sqrt{\frac{\Delta l}{g}}$$