During the study it was noticed that shear strain per unit time changes, as the tangential force (per unit area) applied on the shear stress and shear rate
Answers
Surface tension is a property of liquids which is felt at the interface between the liquid and another fluid (typically a gas). Surface tension has dimensions of force per unit length, and always acts parallel to the interface. Surface tension causes the molecules at the interface to repel each other, forming a kind of "skin" under tension at the interface. A good example of surface tension is found in a common soap bubble. A soap bubble is a good example to illustrate the effects of surface tension. How does a soap bubble remain spherical in shape? The answer is that there is a higher pressure inside the bubble than outside, much like a balloon. In fact, surface tension in the soap film acts much the same as the tension in the skin of a balloon. Consider a soap bubble of radius R with internal pressure pin and external (atmospheric) pressure pout. If the area shown is magnified, a free body diagram of the soap film can be drawn.
On the free body diagram, the sum of all forces must be zero, since the soap film segment is not accelerating. Surface tension forces act parallel to any interface. On the free-body diagram of the soap bubble segment, there are four locations where surface tension acts, as shown. Analysis of a soap bubble yields the following,