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"Gravityless" Capillary tube

  • #1
113
34

Homework Statement


A 20 cm long capillary tube is dipled in water.The water rises up to 8cm .if the entire arrangement is put in a freely falling elevator ,the lenght of the water column is

A)10cm

B)8cm

C)20cm

D)4cm

Homework Equations


Its a theoretical sum

The Attempt at a Solution


Okay...since this is a freely falling elevator ,the reletive accelaration will be zero and hence i feel the fluid will maintain its orignal height of 8cm

But alas ,the book says its 20cm and have give the reason that since its "gravityless" ie :rel accelaration 0, it will occupy full capillary tube.

[Edit 1 -fixed a typo
Edit 2 - i wrote about what i did in Edit 1]
 
Last edited:

Answers and Replies

  • #2
Chandra Prayaga
Science Advisor
649
148
What are the forces acting on the column of water in the capillary before you put it in the elevator? What force is pulling the water up the capillary against gravity?
 
  • #3
113
34
What are the forces acting on the column of water in the capillary before you put it in the elevator? What force is pulling the water up the capillary against gravity?
Oh !!! I think i got it !!!
Case 1
Alright ,so before we put the fluid in the elevator we have forces of adhesion pulling water up the capillary tube,but one it reaches a certain hieght ,force of gravity dominates and hence it cant go further

Case 2
During free fall there is nothing to stop the liquid from rising ,that is ,due to adhesion the liquid continues to rise until it occupies full cappilary tube !!!
 
  • #4
113
34
Hence the answer should be 20 cm right ???
 

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