If we dip our fore finger in water and we try to pull it out we notice that our forefinger sort of 'drags' the water along with it(see pic).My textbook says its because of surface tension and leaves it there.I am however unable to understand why so.The surface tension in my opinion will try to pull back (downward force) and hence try to detach from our finger.Is the reason for this 'drag' is because of the adhesive force btw our finger and water greater than force by surface tension and hence the finger drags the water along with it?. I am having a bit difficulty to comprehend whats happening......

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1 Answer 1


The surface tension effect can be understood from the picture below (figure source).

Surface tension

There are three components of the surface tension. Mostly people think about the surface tension between water and air, but there is also surface tension between your finger and air, and your finger and water. Together with gravity this defines the contact angle at the interface. If the droplet is small, the surface tension is stronger than gravity. This is why you can tilt the water up, or why droplets attach to surfaces.

I am not sure what the adhesive force would be that you are hypothesizing about. You can experiment with bigger surfaces, since an adhesive force would scale with area, whereas the surface tension force scales with the circumference mostly.


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