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...
I'm a Game developer and frankly I must say that you don't need a lot of math and very little physics. All I used so far are Trigonometry,Linear Algebra (for 3d matrices) and some interpolations. I woudn't really say that's complicated math. As for physics some knowledge about mechanics and forces should help if you want to simulate the environment but otherwise I woudn't really see the point.  

I also did some other applications in my spare time never needed any math that's over 8th grade.