Paper Clip Float On Water
Nosotros know that a metal paper clip floats on h2o when it is carefully placed over the surface. This is attributed to the phenomenon of surface tension. I understand that, due to its weight it creates a depression in the fluid as seen in the image below:
Paradigm source: Wikipedia
Due to this depression, there exists a vertical component of the otherwise horizontal force which supports the weight of the newspaper clip and ensures information technology stays on the surface. This is similar to placing a metallic ball on a flexible rubber sheet. The following diagram shows a cross section of the paper clip and the forces interim on it:
Paradigm source: My ain work :)
I've learnt that the bending between the tangent planes at the solid surface and the liquid surface at the betoken of contact, is defined as the contact angle. Hither it's $\theta$ and is obtuse. However, I've seen from different sources that metallic-water contact angle is astute even in the presence of some surface contaminants, totally opposite to what is expected if it needs to be on top of h2o. The following statement is one such example:
Hydrophilic metallic surfaces (copper, nickel) are completely wetted by water only if the surfaces are extremely make clean. Surface contamination reduces the wettability drastically. Under most industrial conditions advancing contact angles betwixt 40° and 80°, and receding contact angles smaller than xx° tin be expected, and the contact angle hysteresis is large.
Source: The wettability of industrial surfaces: Contact angle measurements and thermodynamic analysis
Even though the above quote is for metals like copper and nickel, I think, fifty-fifty aluminium and fe (of which newspaper clips are made of) testify a similar behaviour. If so, why does a metal newspaper clip float on acme of water? Shouldn't it but sink if there were no surface tension? Or is the birdbrained contact angle (observed) related to the difference in contact angle well-nigh the summit of a capillary tube of insufficient length?
Since we notice obtuse contact angle for an interface which ought to have an acute contact angle, will the consequence be same if nosotros consider the other case? Or in other words, volition a paper clip made of an ultrahydrophobic fabric (contact angle $>150^\circ$) float when placed on water?
If the normal newspaper clip had an obtuse contact angle, I wouldn't accept had this doubt. The post-obit argument from this reply to the question - How does surface tension enable insects to walk on water?, resonates with my idea of floating hydrophilic paper clips and sinking metal paper clips (the latter is not true as per our observations):
It is non simply the water-air surface tension that allows the insect to walk on water. Information technology is the combination of the legs non being wetted and the surface tension. The legs of water striders are hydrophobic.
Then, it would exist very helpful if you could explain why does a metal paper clip bladder even though it has an acute contact angle with water.
Delight note that the question Surface tension: the paper clip experiment is not aforementioned as this i. It doesn't discuss about the birdbrained contact angles observed between metal newspaper clip and water which is the central theme of this question.
Paper Clip Float On Water,
Source: https://physics.stackexchange.com/questions/555199/why-does-a-metal-paper-clip-float-on-water-despite-having-an-acute-contact-angle
Posted by: mossgess1946.blogspot.com
0 Response to "Paper Clip Float On Water"
Post a Comment