There is another whole category of questions to be considered,
namely questions that require outside-the-box thinking. Some
examples include:
-- The "nine dots" puzzle. This is the archetype and eponym
of outside-the-box puzzles.
-- The "fox + duck + grain" puzzle. The direct approach doesn't
work.
-- There is an orchard with 10 trees in five straight rows of
four trees each. Explain.
++ Et cetera.
These examples have little to do with physics /per se/, but
maybe that's a good thing. They teach general-purpose thinking
skills that can be applied to physics and everything else. At
this point in the year, the students don't have enough physics
domain knowledge to permit much in the way of physics puzzles
/per se/ ... so in the meantime it is useful to give them some
puzzles they can handle, to exercise ye olde thinking muscle.
Besides, these puzzles are fun. And they are incomparably
easier than some of the other puzzles that we have been
discussing recently.