One rule for three oscillators

You will write the period of three oscillators that are not simple pendulums.

The idea. Each one has a pull back in proportion to the displacement. A liquid column of length $L$ in a U-tube has $T = 2\pi\sqrt{L/2g}$. A body floating with depth $h$ under water has $T = 2\pi\sqrt{h/g}$. A rod of length $L$, hanging from a hole $d$ from its middle, has $T = 2\pi\sqrt{\dfrac{L^2/12 + d^2}{gd}}$.

Your tasks.

1. In period_u_tube, return the period of the liquid column, in s.
2. In period_float, return the period of the floating body, in s.
3. In period_rod, return the period of the rod, in s.