surface tension
We’ve seen that if an object is less dense than water, it will float partially submerged.
But a paper clip can rest atop a water surface even though its density is
several times that of water. This is an example of surface tension: The surface
of the liquid behaves like a membrane under tension . Surface tension
arises because the molecules of the liquid exert attractive forces on each
other. There is zero net force on a molecule within the interior of the liquid, but a
surface molecule is drawn into the interior (Fig. 12.15). Thus the liquid tends to
minimize its surface area, just as a stretched membrane does.
These Topics Are Also In Your Syllabus | ||
---|---|---|
1 | Gravitation and spherically symmetric Bodies | link |
2 | Determining the value of G | link |
You May Find Something Very Interesting Here. | link | |
3 | EXAMPLES ON GRAVITION | link |
4 | Why Gravitational forces are important | link |
5 | Types Of Systems | link |
These Topics Are Also In Your Syllabus | ||
---|---|---|
1 | FLUID FLOW | link |
2 | The Continuity equation | link |
You May Find Something Very Interesting Here. | link | |
3 | Bernoulli's equation | link |
4 | Deriving Bernoullis equation | link |
5 | Types Of Systems | link |
Surface tension explains why raindrops are spherical (not teardrop-shaped):
A sphere has a smaller surface area for its volume than any other shape. It also
explains why hot, soapy water is used for washing. To wash clothing thoroughly,
water must be forced through the tiny spaces between the fibers (Fig. 12.16). This
requires increasing the surface area of the water, which is difficult to achieve
because of surface tension. The job is made easier by increasing the temperature
of the water and adding soap, both of which decrease the surface tension.
These Topics Are Also In Your Syllabus | ||
---|---|---|
1 | finding and using the Center of gravity | link |
2 | solving rigid-body equilibrium problems | link |
You May Find Something Very Interesting Here. | link | |
3 | SOLVED EXAMPLES ON EQUILIBRIUM | link |
4 | stress, strain, and elastic moduLi | link |
5 | Types Of Systems | link |
These Topics Are Also In Your Syllabus | ||
---|---|---|
1 | Pressure in a fLuid | link |
2 | pressure, depth, and pascals Law | link |
You May Find Something Very Interesting Here. | link | |
3 | PASCAL LAW | link |
4 | absolute Pressure and Gauge Pressure | link |
5 | Types Of Systems | link |
Surface tension is important for a millimeter-sized water drop, which has a
relatively large surface area for its volume. (A sphere of radius r has surface area 4pr^{2 }and volume (4p/3)r^{3}
. The ratio of surface area to volume is 3/r, which
increases with decreasing radius.) But for large quantities of liquid, the ratio of
surface area to volume is relatively small, and surface tension is negligible compared
to pressure forces. For the remainder of this chapter, we’ll consider only
fluids in bulk and ignore the effects of surface tension.