The derivative with respect to time is indicated with a dot over the quantity; a second derivative is indicated with two dots, etc. You can think of this as similar to the "prime" notation for derivat...The derivative with respect to time is indicated with a dot over the quantity; a second derivative is indicated with two dots, etc. You can think of this as similar to the "prime" notation for derivatives encountered in calculus, except that the "dot" over a variable always indicates a derivative with respect to time. The "prime notation" sometimes used (x′(t), x′′(t), etc.) is due to Italian mathematician Joseph-Louis Lagrange.
