Like in this figure we see that the surface molecules have a net downward force to all of these so should any force which we made along a line on the surface the force be downwards ? Why the surface tension is parallel to the surface ? 
Why surface tension direction cannot be downwards in direction when considered the surface of fluid?
$\begingroup$
$\endgroup$
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
3
The existence of a surface with unsatisfied bonds produces an energy penalty. This results in an internal Laplace pressure, an increase in the chemical potential of the system, and a resistance to increasing the surface area: the surface tension. Since you'd apply a force parallel to the surface to extend the area, as shown below, the corresponding restoring force is also parallel to the surface.
answered Jan 27, 2022 at 18:59
-
$\begingroup$ Sir i got you point but then why in textbooks they first describe about the downward force on surface molecules while explaining surface tension ? $\endgroup$ Commented Jan 27, 2022 at 19:04
-
$\begingroup$ I can’t really speculate on the motives of an unknown textbook, but people have indicated that this review of the topic is useful. See also this question. $\endgroup$ Commented Jan 27, 2022 at 20:21
-
$\begingroup$ Thanks Sir it was really useful $\endgroup$ Commented Jan 28, 2022 at 2:01
$\begingroup$
$\endgroup$
1
Its a little like the definition of friction. The force components parallel to the surface are called the surface tension. The downward component is what works against evaporation.
