ok.. i just had physics class today and the same question was asked!1 divided by infinity equals zero
dont argue..
Dont take this personal - but have you stopped to think it over yourself? Not all physics teachers know everything (I had this argument with my maths lecturer on something similar). Their are at least 5 types of infinity. The two that spring to mind (alpha null?) are what confuses people the most. The first is continuous numbers e.g. 1+1, etc..The second is the type of infinity that as soon as you start to to imagine how big it is - your wrong its infinitesimally bigger (big word - bad spelling, probably).
The question was does 1 divided by infinity = 0 the answer is no - unless you disregard the infinite number of decimals places and set a significant digits no. so the answer will be be more zero than 1 but it still wont be exactly 1. The same applies to the circle an infinite amount of polygons might look like a curved surface but it isnt its just almost their.
So basically 0.0000000000000000000000000000000000000000000000000000000000000000000000000000001 is not zero but its close, and if your only looking for an answer to within the odd million digits then it will appear to be zero - but only because you have set a limit (which you cant when thinking of infinity).
The main problem with both of these is that you cant calculate infinity its just not possible and so when doing any sort of calculation based on infinity you have to assume its 0 and as the error is so minute it 'shouldnt' make to much of an error.
Side note - if this comes over badly sorry I have asberger's and my 'speciality' is practical physics.