# Do dimensions of the product $q_k p_k$ always equal to that of angular momentum?

I know that generalised coordinates and their conjugate momentum may or may not have the same dimensions as to that of length and linear momentum, but in one book I saw it was mentioned that their product must always have the dimensions of angular momentum.

Is it true?

• If you like this question, you may also enjoy reading this & this posts. – Qmechanic Sep 1 '17 at 8:20

The Lagrangian $L$ has dimensions of energy, and $$p_i=\frac{\partial L}{\partial \dot{q}^i},$$ so (because $\dot{q}$ has dimension of $[q]/T$) $$\frac{[q]}{T}\cdot[p]=E, \\ [q]\cdot[p]=E\cdot T.$$
And $E\cdot T$ is precisely the dimension of action/angular momentum.