I have read oodles of physics textbooks and have come across many topics that are rarely discussed correctly or clearly (at least in my opinion). Here are some of my favorites. 1. Impulse. Authors continually ascribe the impulse to an individual force, not a net force. Why? The force in the equation [tex]\Delta p = F\Delta t[/tex] is clearly the net force. 2. Systems, such as the rocket ship, that supposedly change mass, producing some mysterious force that has no definable source. Nope, not in my book. 3. Reversible/irreversible cycles. I have seen these two issues screwed up on many occassions. At some point I begin to wonder if the authors really understand thermodynamics. 4. Work/energy. Most authors do not have a clear, uniform way of relating conservative and non-conservative forces to changes in energy. 5. Too many equations. You should only need about a dozen equations to cover the entire first semester of classical physics. Any more than that simply confuses the students. Any others?