Capillary rise-conceptual

  • Thread starter sowmya2010
  • Start date
  • #1
sowmya2010

Homework Statement



A capillary is dipped in water vessel kept on a freely falling lift, then

a)water will not rise in the tube
b)water will rise to the maximum possible height of the tube

Homework Equations



W=2[tex]\pi[/tex]r S cos[tex]\theta[/tex]
or h=(2S cos [tex]\theta[/tex])/(r[tex]\rho[/tex]g)

The Attempt at a Solution



as this is the case of free fall g tends to 0 hence h tends to infinity hence the option (b)

but it might also mean that cos [tex]\theta[/tex]=0, i.e, the water doesn't rise at all, hence the option (a)

which logic is correct?
 

Answers and Replies

  • #2
960
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Just an educated guess here, as no one else is around--but the way I see it the tendency to minimize surface area and hence form some angle theta is a function of surface tension which is independent of weight. The capillarity (attraction to the glass and consequent pull up the side is also present. OTOH, what happens to the weight of the water as it free falls?
 
Last edited:
  • #3
77
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I'm guessing here too, but I'd imagine it'd rise to the top of the tube, as the molecular forces responsible for the surface tension are still present, but the water has no effective weight as the lift is in free fall, therefore there will be a net upward force which will pull the water up the tube.
 
  • #4
mukundpa
Homework Helper
524
3
And on outer surface as well, I think
 

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