Crimes Against Physics: Pitfalls that will Drive your Physics Teacher Nuts and make a Clown of You

These are mistakes that new physics students make. We will explore them and learn how to avoid them.
(1) Thinking that g should be -9.8.
(2) Thinking that the final velocity in a kinematics problem is zero if an object hits the ground.
(3) Making up a fictitious "force of the acceleration."
(4) Thinking of a centripetal force as an extra, magical type of force that should be drawn in a free body diagram and considered.
Indeed issues (3) and (4) can he handled by transforming to a different reference frame, but new students rarely do this correctly and tend to generate incorrect solutions with that technique.