Find the first and second derivatives with respect to what
If you want to find the derivatives with respect to Q (what you appear to be doing), then t is just treated as a constant.
If you are asked to find all
first and second partial derivatives, then there are two first order derivatives,
, and four (though two of them will be the same) second order derivatives,
Each partial derivative with respect to the given variable, is taken exactly like an ordinary derivative, treating the other variable as if it were a constant.