1
$\begingroup$

enter image description here

I was observing a leaky tap today and I noticed that when I poked the approximately hemispherical surface developed before the water dropped, the water quickly came off as a stream.

If I don't disturb it, the leaky tap would drop out water droplets periodically in some time interval.

Why does the poke lead to a stream of water to gush out of the tap while otherwise it is periodic drops?


I do understand the surface tension going on here. I am just asking why when I poke the water falls through, while the other cause it goes drop wise. Like, after the water drop falls, it seems again the surface is reformed before it breaks, while in the other case there is no reformation of surface and the liquid just keeps pouring.

$\endgroup$
1
$\begingroup$

It happens because of surface tension. The water tends to have the smallest possible surface area to minimise the surface energy and holds together the water drops. When you poke the film, i.e. the interface between air and water, you let the water droplets come out at once. The adhesive force between your fingertip and the water is greater than the cohesive forces between the water molecules, and your touch ruptures the film. So water starts pouring all at once. However, if you let the leaky faucet alone, the water keeps on accumulating slowly, and the water droplet breaks away when the weight of the drop overcomes the force due to surface tension. The disruption is not enough to rupture the film completely, and it stays.

$\endgroup$
1
  • $\begingroup$ I have edited the question $\endgroup$
    – User688539
    Sep 22 at 10:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.