  We study sharp second order inequalities of Caffarelli-Kohn-Nirenberg type in
the euclidian space $\mathbb{R}^{N}$, where $N$ denotes the dimension. This
analysis is equivalent to the study of uncertainty principles for special
classes of vector fields. In particular, we show that when switching from
scalar fields $u: \rr^n\rightarrow \mathbb{C}$ to vector fields of the form
$\vec{u}:=\nabla U$ ($U$ being a scalar field) the best constant in the
Heisenberg Uncertainty Principle (HUP) increases from $\frac{N^{2}}{4}$ to
$\frac{(N+2)^{2}}{4}$, and the optimal constant in the Hydrogen Uncertainty
Principle (HyUP) improves from $\frac{\left( N-1\right)^{2}}{4}$ to
$\frac{(N+1)^{2}}{4}$. As a consequence of our results we answer to the open
question of Maz'ya (Integral Equations Operator Theory 2018) in the case $N=2$
regarding the HUP for divergence free vector fields.
