[Hindi] Why water droplets are spherical? – Surface Tension [English subs]

[Hindi] Why water droplets are spherical? – Surface Tension [English subs]


water droplets take such beautiful spherical shapes You must have seen this shape of water droplets for instance the last few drops from a tap or on leaves after a cold night The reason for this is Surface Tension the surface tension can vary between different liquids but its effect in water can be seen all around us which motivates us to learn this phenomena with some cool experiments What exactly is surface tension? Think of a container with water. Now let’s consider a water molecule inside it. Around this molecule other water molecules are evenly distributed Now this center molecule is evenly attracted by other molecules surrounding it so what is the net force acting on this center molecule? zero Now let’s consider a water molecule at the surface This molecule has water molecules on its left, right & below but there are no water molecules above it so this molecule is attracted down and to its sides but no attractive force from above So which direction will be the net force on this molecule? downwards.. And because of this this entire surface is pulled downwards This phenomena is called Surface Tension Now this surface behaves as a stretched membrane since the force acting on the surface water molecules is non-zero A stretched membrane always tries to minimize its surface area Let us consider a set of 3-D objects like sphere, cone, cylinder, all of the same volume Now mathematically we can show that among all the 3D objects Sphere has the minimum surface area Now that’s why due to surface tension- water droplets take spherical shape Chatur!! What’s this?! If it behaves like a stretched membrane.. can it support weight? We will try to find its answer with the help of an experiment Now we will try to put this metal clip on the surface of water very carefully Isn’t it surprising? In spite of having higher density than water this metal clip can rest on water surface This is possible as the water surface behaves like a stretched membrane If a part of the metal clip goes inside the water then it will sink And that’s the reason some insects can walk on water! And maybe some movie stars?!! Another interesting thing happens when we put a drop of liquid soap on the water Chatur! Having fun?! Now we will do another experiment which you can show off to your friends We have cut a big hole on the lid of this jar after that we have cut a big piece off a strainer we fixed that piece on the jar using the lid now we will pour some water on this This trick was possible because of surface tension and as you saw, even a needle couldn’t break that surface tension After all these experiments, we now have a better understanding of surface tension but this question certainly arises how this understanding can come off any use? certainly!! car wind shields are given a coating so that rain water doesn’t stick to it so that we can have clear vision This application was discovered only when surface tension was well understood Don’t forget to Like & Share this video. Also don’t forget to subscribe to your channel for more exciting videos like this Can you tell us why water leaks out of the jar when you tilt it? Let us know in the comment section

16 Replies to “[Hindi] Why water droplets are spherical? – Surface Tension [English subs]”

  1. On tilting, the volume of water takes the shape of a cone. So the water molecules are not uniformly distributes hence the net force on the molecules at the vertex of the cone is not zero and that is why the water falls out.

  2. Due to increase in surface area the surface tension decreases and hence on tilting the water falls down from the container

  3. Water falls down, while tilting the jar , because the surface tension of the water molecules decreases..!

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