I really don't care, so I voted that, even if I'm not a fan or beer nor of pretzels.
Actual physics apply as normal. Yay! That means you could make gunpowder or particle accelerators if you had a valid reason to discover how to make one.
But while physics laws apply, it is not the only thing that apply.
To make a comparison, gravity apply, yet you can make things fly through other forces (like magnetism) or mechanical efforts (see any type of planes) or even by making gravity works for you (lighter-than-air crafts or orbital stations).
In a world with magic, it's the same for everything, at a larger scale. The five physical forces (electricity, magnetism, strong nuclear, weak nuclear, gravity) exist. But they are far from the only ones. There are several magical and philosophical forces that apply as well, and can result in a lot of divergence compared to what our world looks like.
Take Earth, and imagine how it would look like if, say, there were no electromagnetism. For a start, life would be very different, if it would even exist without the protection of Earth's electromagnetic shield. Assuming somehow a civilization appears, it wouldn't use radio, computers, or everything else we use continuously in our daily life.
Instead of removing electromagnetics, remove, say, gravity -- blam!, no planets, no stellar systems, no galaxies even! Just a infinite limbo with an even, homogenous distribution of microparticles.
Now that you can see the drastic changes removing one force can have on the destiny of an universe, you can see that our own real world is drastically changed from an universe with additional forces. For convenience, these extra forces balance each others just enough to let us play in a D&D setting -- close enough from what we know to let us understand the world quickly.
But really, I could care less about all those complicated and convoluted theories about how should a setting be if it were Earth's "separated-at-birth" twin sister, with a blatant lack of magic, gods, flying dragons, fiends, inner and outer planes, and 287 competiting sentient races each with their own civilization, all intermingled.
Just like a magnet can stick on a fridge's door indefinitely despite everything that gravity-enthusiasts can tell you about how it should logically falls down and how it feels just wrong to have something stays against a vertical surface without falling, a D&D setting doesn't have to concern itself with the so-weak-to-be-negligible-compared-to-others forces of plate tectonics, climatology, and economical theories. (Especially given that modern-day economical theories are all about as exact as medical theories were in the 17th century -- "whatever ails him, a good bleeding and he shall feel fine!"...)