(adsbygoogle = window.adsbygoogle || []).push({}); 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.

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# Homework Help: Surface tension question

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