Writing good word problems is very hard.
One that drove me nuts, and still sticks with me is:
"Consider two identical stars revolving around each other..."
He meant the orbits have the same center, but if you don't realize that instantly, you'll be going off down a rabbit hole - at least I was. :-/
The work, force, and kinetic energy problem is just one example of how things can be obscured by the way physics is taught (at least in the US). Too much of it is all about finding the "tricks" and knowing which equation to apply and how to simplify it. Too little is about clarity in definition of the terms and getting students to the "ah ha!" moment when it finally clicks.
In '83 or so when I was finishing up my college classes and thinking about what to study in grad school, I had some sessions with a TA who was studying for his physics qualifier exam (one of the hurdles to jump before being allowed to write a dissertation). He was going through one of the standard problems that everyone had to be able to do there: Write the equations of motion for a top spinning on a spinning globe and determine various things given their sizes and the friction between them. It turned me off immediately.
Yeah, being able to do advanced mechanics problems like that was something I'd likely never have to do again (though there are exceptions - someone had to figure out the equations of motion of the planets and the rockets that went to the moon and related problems - http://link.springer...0.1007/BF02715967 ), and sometimes things like that are designed to be weeding-out problems rather than something that one really should "know". And someone being able to know enough about it to teach it to the next generation is important if you're interested in teaching. But it didn't appeal to me. (I knew I wanted to do research - not teach.)
I have no idea how things are in graduate schools now. Some areas of physics have exploded (solid-state, biophysics, various cosmological theories) while some have changed very little (mechanics). There's more stuff to know that's being crammed into the same standard time frame. I'd hate to think that the same "weeding-out" problems are taught just for historical reasons.
Anyway, I'm rambling.
Before I close, here's the book I was trying to remember. It really should be required reading for those interested in teaching physics - and for those who are seriously interested in trying to simplify physical topics for a lay audience in the hope that they'll want to learn more later.
Arnold B. Arons - "Teaching Introductory Physics" - http://www.amazon.co...ns/dp/0471137073/ (It's spendy, but can sometimes be found for far less used.)