I would not know how to answer a student who might
ask why the displacement is defined as Xfinal-Xinitial
in Chapter 2 and as Yinitial-Yfinal in Chapter 5. I am
referring to Section 5.3 of College Physics (5th edition)
by Serway and Faughn (page 121 etc.).
I suppose this was done to make a change of potential
energy positive while the corresponding change of
kinetic energy is negative, and vice versa. But should
a displacement be always (final-initial)? Something
is not right. What is it?
Ludwik Kowalski