1. The problem statement, all variables and given/known data First part of the question was "Why is it possible to float a wax-coated stainless steel needle on the surface of water?" and I've already answered that, but I'm having trouble with the second part of the question, which is: If the surface tension at the interface is 0.073 N/m and the density of the steel needle is 7.8x10^3 kg/m^3, what is the maximum diameter of a needle that can float this way? (Hint: start by finding the weight of the needle. You may assume that the needle is cylindrical in cross-section) 2. Relevant equations Density = mass / volume h = (2[tex]\sigma[/tex]cos[tex]\Psi[/tex]) / ([tex]\rho[/tex]g[tex]\alpha[/tex]) V of needle = width x (2[tex]\Pi[/tex]r^2) I'm actually not too sure which equations I need... 3. The attempt at a solution [tex]\sigma[/tex] = 0.073N/m [tex]\rho[/tex] of stainless steel needle = 7.8x10^3 kg/m^3 Well it says to start by finding the weight of the needle, and I wasn't sure how to approach that in the first place, so I wasn't able to make a start.