- A$11.96$
- B$2.34$
- C$8.24$
- ✓$5.34$
Radius of the narrow tube, $r=1 mm =1 \times 10^{-3} m$
Surface tension of mercury at the given temperature, $s=0.465 N m ^{-1}$
Density of mercury, $\rho=13.6 \times 10^{3} kg / m ^{3}$
Dip in the height of mercury $=h$
Acceleration due to gravity, $g=9.8 m / s ^{2}$
Surface tension is related with the angle of contact and the dip in the height as
$s=\frac{h \rho g r}{2 \cos \theta}$
$\therefore h=\frac{2 s \cos \theta}{r \rho g}$
$=\frac{2 \times 0.465 \times \cos 140}{1 \times 10^{-3} \times 13.6 \times 10^{3} \times 9.8}$
$=-0.00534 m$
$=-5.34 mm$
Here, the negative sign shows the decreasing level of mercury. Hence, the mercury level dips by $5.34\; mm$
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.


(Sp. heat of water $1\,cal/gm$, Specific heat of ice $= 0.5\,cal/g\,^oC$ , letent heat of fusion $= 80\,cal/g$ )