$3.2.5.$ Find the length of a mathematical pendulum with an oscillation period of $1$ s.
The period of oscillation of a mathematical pendulum $$ T=2\pi\sqrt{\frac{l}{g}} $$ Where does the length of the pendulum come from? $$ l=\frac{T^2g}{4\pi^2}=24.8\text{ sm} $$
$$l=24.8\text{ sm}$$