Q.

An open-ended U-tube of uniform cross-sectional area contains water (density 103 kgm-3). Initially the water level stands at 0.29 m from the bottom in each arm. Kerosene oil (a water-immiscible liquid) of density 800 kgm-3 is added to the left arm until its length is 0.1 m, as shown in the schematic figure below. The ratio (h1h2) of the heights of the liquid in the two arms is                           [2020] 

1 1514  
2 3533  
3 76  
4 54  

Ans.

(2)

Pressure will be same at the same horizontal level.

  PA=PB

P0+ρkg×0.1+ρwg×(h1-0.1)=ρwgh2+p0

80+1000(h1-0.1)=1000h2

80+1000h1-100=1000h2

h1-h2=201000

h1-h2=0.02        (i)

Also, h1-0.1+h2=2×0.29

h1+h2=0.68             (ii)

Solving (i) & (ii), we get

      2h1=0.70

   h1=0.35 m

and h2=0.33 m

So, h1h2=3533