60 frames/second (simulation rate, not graphical drawing rate). Some of the numbers I estimated myself, some I found out by asking people.

BTW, the formula used to calculate position after n frames(n > 0) is something like:

p(n) = p(0) + v(0) + (v(0)*(d^(n) - d)/(d - 1)) + (f/(d - 1))*((d^(n+1) - d)/(d - 1) - n*d)

This may be incorrect, as I'm pulling partly from memory and partly from a broken version I made, since I can't find my correct version. This is done independantly for X and Y, only for X the value of f is 0, while for Y it's the value of gravity. d is a dampening value.

Formula for velocity after n number of frames (n>0) is something like:

v(n) = (v(0) * d^(n-1)) + f * ((d^(n) - d)/(d - 1))

Again, going off some old broken stuff + memory to fix it, so might not be 100% correct.

Yes, Polyworks uses pixels.