Physics · 2019
JEE Main · 10 April 2019, Shift 1 · Q9
The ratio of surface tensions of mercury and water is given to be 7.5 while the ratio of their densities is 13.6. Their contact angles, with glass,…
The ratio of surface tensions of mercury and water is given to be $\displaystyle 7.5$ while the ratio of their densities is 13.6. Their contact angles, with glass, are close to $\displaystyle 135^{\circ}$ and $\displaystyle 0^{\circ}$, respectively. It is observed that mercury gets depressed by an amount $\displaystyle h$ in a capillary tube of radius $\displaystyle \mathrm{r}_1$, while water rises by the same amount $\displaystyle h$ in a capillary tube of radius $\displaystyle \mathrm{r}_2$. The ratio, $\displaystyle \left(\mathrm{r}_1 / \mathrm{r}_2\right)$, is then close to :
Official answer
(1)
$\displaystyle 2$/$\displaystyle 5$
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JEE Main 2019 Physics question, with the answer from NTA’s final answer key. Where our answers come from.