One might say a problem of physics becomes philosophical when it is a question too diffcult to answer with the mathematical & physical technology then at hand.
Jerrold Zacharias began by developing a series of physics demonstration films to be distributed to high schools. The films would not only show novel physics experiments, but also show , not as white-haired savants but as regular, hard-working, inquisitive human beings. The NSF provided funding for Zacharias to launch a broader investigation into physics curricula, known as the Physical Science Study Committee (PSSC), where Zacharias and a host of other physicists and scientists -- many of them from MIT -- would attempt to "solve" the problem of physics education in the United States.
The problem of physics Performance - HTML5 Game Devs Forum
Before anyone else, Einstein recognized the essential dualism in nature, theco-existence of particles and waves at the level of quanta. In 1911 hedeclared resolving the quantum issue to be the central problem of physics.