Question: In what particular situation you will need a depth knowledge of math/physics in software engineering?

Answer: 
Depends a bit on your line of work. If your trying to implement some kind of gravitational model for a game engine, knowledge of physics will surely help. 

I think knowledge of math is required however, you will always encounter some problems that have to do with mathematics. For instance, I work as a web developer; for one client we had to make a tool/feature on his website that calculates distances between to places. But the programmer didn't know how to implement/use Pythagoras theorem...
For programming itself: it is helpful to come up with relations and functions, but no depth knowledge is needed. If you wan't to deal with deeper questions and more theoretical stuff: yes, it is math. Physics is not needed, unless you want to solve a physics problem of course.