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Simple fluids but is the application correct

  • #1

Homework Statement



problem states that .... there is a u tube and filled with liquid of densities ρ and 2ρ. the base lenght of the tube is 'l'. now it is accelerated towards right with accl.=a. if the HEIGHT DIFFERENCE AFTER ACCELERATING THE SYSTEM IS '0'. then what was the height difference before acceleration??

Homework Equations



P=ρgh; F=ma ; F=(ρ.V)a ;

The Attempt at a Solution


i tried to find pressure at bottom most level at interface of the two liquids, then the net force, then applied newtons 2nd law, but could'nt get the solution...

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
tiny-tim
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hi phyeinstein_c! :smile:

hint: what will be the angle of the surface of the fluid (in either half of the 'U') ? :wink:
 
  • #3
lets see...if the u tube is moving towards right the major driving force is on the left side of the tube. since the heights are equal the 2p liquid is in the left tube .

first find relations between height h1 and h2 in the two sides of tube when at rest...then find height h when accelerated.. then keeping volume constant use h1 + h2 = 2h
 
  • #4
hi phyeinstein_c! :smile:

hint: what will be the angle of the surface of the fluid (in either half of the 'U') ? :wink:
they're not at angle. initially they are at a height difference. thats it is wat is given.
 
  • #5
tiny-tim
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i know, i mean, suppose there was only one pipe (or a jar or vase), what would be the angle of the water surface? :wink:
 
  • #6
it wud be horizontal obviously
 
  • #7
tiny-tim
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nope! :wink:
 
  • #8
why...???
 
  • #9
tiny-tim
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suppose the water was ice, and the surface was at an angle, and a drop of water was on the surface …

what angle would the surface have to be for the drop of water to stay where it is? :wink:
 
  • #10
<=45 i guess
 
  • #11
tiny-tim
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  • #12
:P just guessing... mgsinθ is equal to the friction acting.. of surface tension watever... unless u describe the surface of ice to be smooth....
 
  • #13
tiny-tim
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… unless u describe the surface of ice to be smooth....
yes, of course it's smooth! :rolleyes:
 
  • #14
ok... then it cant stay where it is..
 
  • #15
tiny-tim
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why not?

(if the block of ice is accelerating)
 
  • #16
oh yeah thats there... true.. then we can find the component of ma and normal reaction in horizontal direction and solve..
 

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