Yesterday I chaired the selection committee to choose the student who will be hired in the AMVA4NewPhysics network
by the Padova section of INFN, and during the interviews I asked all candidates a couple of "easy" physics questions, meant to test the students' reasoning process rather than their prior knowledge.
The first question was only apparently easy - even too much, from the outset. The fact is, the devil is always hiding in the details, as I immediately realized as I tested it by asking an experienced colleague to answer it. He got part of the question wrong, but in doing so he clarified to me that there was a non trivial aspect below the surface.