Today was the last class for my HL group. This year we finished the syllabus early (yesterday) so had time for some exam question practice. The last topic was relativity which I think they enjoyed. Maybe it's the last time that I teach that option, engineering physics being the obvious choice in the new course. As an example of the principle of equivalence I showed how we can find the angle of an accelerating bucket of water by the vector addition of the gravity plus the "equivalent gravity" of the acceleration, a nice little example. A free falling frame of reference is however equivalent to an inertial frame, until you hit the ground that is. So let's do some free fall....

Students today just don't have the restitution.