I've had a coding interview (screen, not whiteboard) fail where the main criticism was that one routine detail I took a while to get right could have been googled faster. In hindsight I still doubt that, given all the semi-related tangents you end up following from Google, but that was their expectation, look up the right piece of example code and recognize the missing bit (or get out right immediately).
For a proper engineering question (as in not software), I'd expect the expected answer to be naming the reference book where you'd look up the formula. Last thing you want is someone overconfident in their from memory version of physics.
> Last thing you want is someone overconfident in their from memory version of physics.
Honestly, having been in both worlds, there's not too much of a difference. Physics is harder but coding you got more things to juggle in your brain. So I really do not think it is an issue to offload infrequent "equations"[0] to a book/google/whatever.
[0] And equations could be taken out of quotes considering that math and code are the same thing.
For a proper engineering question (as in not software), I'd expect the expected answer to be naming the reference book where you'd look up the formula. Last thing you want is someone overconfident in their from memory version of physics.