MadSci Network: Physics |
Answer: Yes, assuming the tube is of a "normal enough" material like glass and the tube is inserted in a spaceship, a case of presence of air but no gravity.
Why: There are some basic things to understand before we go ahead with understanding why this would happen.
Firstly, we need to understand a phenomenon called "WETTING"
which is observed
on the interface between solids and liquids. When a liquid is brought in
contact with a solid, a curvature is observed in the liquid surface
(meniscus)
near the solid surface. This curvature is characterised with an angle
called
"ANGLE OF CONTACT" (call it
The origin of this phenomenon is related to SURFACE TENSION, and in turn on
cohesive and adhesive forces. One can find details on this in any standard
good physics book: Resnick and Halliday used to be one of my favorites.
Now, in this respect let us compare things in space vis-a-vis that at
earth.
There are two cases:
1. in a spaceship (no gravity, normal pressure). In this case since there
is
only an absence of gravity, the attractive force in the direction of the
open
end of the tube shall still exist. Thus the water will rise TILL THE TOP OF
THE TUBE. At the top it shall slightly flatten out, id est will not have a
speherical shape as expected.
2. outside the spaceship (no gravity, almost zero pressure). In this case,
the
surface tension of water shoots up. Since the surface tension of the
solid-vacuum interface has almost the same value, I THINK that
that the water will hardly rise. It would behave somewhat like a very
cohesive liquid. Still I am a bit unsure about this. If you want a further
expln. it
is given in below. If you don't want to read too much mathematics right
now,
you needn't go further.
The pressure gradient introduced as a result of wetting is given by:
p2-p1=2*gamma/R (1)
where gamma is the surface tension of the interface and R is the radius of
curvature of the spherical shape the liquid takes up in the capillary.
Now refer to the figure (FIG1) attached. Three gamma values are important
at
the solid-liquid-gas interface. These have been indicated in the figure.
The
equilibrium condition is:
gamma_sol_gas = gamma_sol_liq + gamma_liq_gas * cos(theta) (2)
This relation determines the value of theta. If gamma_liq_gas becomes very
high, as in the present case (in space outside the spaceship), theta
becomes
close to 90 degrees. This means that R in equation 1 becomes very high,
thus
making the pressure differnce very small because of which the water hardly
rises.
REFERENCES: Try R&H, as indicated above. Or try one of the Russian
books on
Physics they are rather good. For advanced readers, you can go to books on
fluid statics and dynamics and look up the index for surface tension.
Try the links in the MadSci Library for more information on Physics.
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