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(D) The net force on a molecule at the surface of the liquid near the glass wall is given by the resultant of the cohesive force $(F_C)$ and the adhes

Vedclass · Accepted Answer

Only $(A), (C), (D)$

Vedclass · Answer

(D) The net force on a molecule at the surface of the liquid near the glass wall is given by the resultant of the cohesive force $(F_C)$ and the adhesive force $(F_A)$.Given $F_C = 2F_A$.The net force $F_{net}$ acts at an angle $	heta$ with the vertical,where $	an 	heta = \frac{F_A}{F_C} = \frac{F_A}{2F_A} = 0.5$.Since the cohesive force is greater than the adhesive force $(F_C > F_A)$,the net force is directed into the liquid,making the meniscus convex.Because the meniscus is convex,the angle of contact $	heta_c$ is obtuse $(> 90^{\circ})$.Liquids with an obtuse angle of contact do not wet the glass surface.The capillary rise or fall is given by $h = \frac{2T \cos 	heta_c}{r ho g}$. Since $	heta_c > 90^{\circ}$,$\cos 	heta_c$ is negative,resulting in a negative value for $h$,which indicates capillary descent.Therefore,statements $(A), (C),$ and $(D)$ are correct.

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