Question

A U-tube is partially filled with water. Oil, which does not mix with water, is next poured into one side, until water rises by 25 cm on the other side. If the density of the oil is 0.8 g/cc, the oil level will stand higher than the water level by

• A. 6.25 cm
• B. 18.75 cm
• C. 12.50 cm
• D. 25.00 cm

Answer 1

The correct option is C

12.50 cm

Let the height of oil column be $x$ and area of cross-section of the tube be $A$.
Density of water = 1 g/cc
Density of oil = 0.8 g/cc
Equating pressure at the bottommost point, $0.8Axg+1A(l-25)g=1A(l+25)g\Rightarrow x=62.5cm$
So, the oil level stands higher than water level by $(l-25+x)-(l+25)=x-50=12.5cm$