The Force
| $$ -\nabla U $$ |
Force from a conservative potential |
| $$ \oint \sigma_{\alpha\beta}\, n_\beta \, \mathrm{d}S $$ |
Net force from stress tensor (no body forces) |
| $$ \frac{\mathrm{d}\mathbf{p}}{\mathrm{d}t} $$ |
Newton’s second law |
| $$ \frac{\partial \mathcal{L}}{\partial q} $$ |
Generalized force from Lagrangian |
| $$ \frac{1}{i\hbar}\langle[\hat{\mathbf{p}}, \hat{H}]\rangle $$ |
Quantum force expectation (Ehrenfest Theorem) |
$$For \,\, my \,\, ally \,\, is \,\, \oint \sigma_{\alpha\beta}\, n_\beta \, \mathrm{d}S , \,\, and \,\, a \,\, power\!ful \,\, ally \,\, it \,\, is. $$