Will the water rise in a capillary when placed on a freely falling lift?

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In summary, the question discusses the behavior of water in a capillary that is dipped in a water vessel on a freely falling lift. The options presented are that either the water will not rise at all (option a) or it will rise to the maximum possible height of the tube (option b). The homework equations provided are W=2\pir S cos\theta and h=(2S cos \theta)/(r\rhog). The attempted solution suggests that the water will rise to the top of the tube due to surface tension and molecular forces, even though it has no effective weight in free fall. Therefore, the correct logic would be option b.
  • #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?
 
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  • #2
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?
 
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  • #3
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
And on outer surface as well, I think
 

What is capillary rise?

Capillary rise is the phenomenon where a liquid rises up through a narrow tube or pore against the force of gravity. This is due to the cohesive and adhesive properties of the liquid, which allow it to climb up the walls of the tube or pore.

How does capillary rise work?

Capillary rise occurs because of the surface tension of the liquid, which creates a concave meniscus at the top of the liquid in the tube. This meniscus creates a force that is strong enough to overcome the force of gravity and pull the liquid upwards.

What factors affect capillary rise?

The main factors that affect capillary rise are the surface tension of the liquid, the diameter of the tube or pore, and the angle of contact between the liquid and the walls of the tube. Other factors such as temperature, gravity, and the type of material the tube is made of can also have an impact.

What are some applications of capillary rise?

Capillary rise has many practical applications, including in plants where it helps to transport water from the roots to the leaves. It is also used in paper towels and sponges to absorb and distribute liquids, and in lab equipment such as capillary tubes and pipettes for precise measurements.

How is capillary rise related to surface tension?

Capillary rise is directly related to surface tension, as it is the cohesive forces between the molecules of the liquid that create the surface tension. The stronger the surface tension, the higher the capillary rise will be. Additionally, a liquid with a high surface tension will have a steeper meniscus, resulting in a greater capillary rise.

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