# NCERT Class 11 Physics Solutions: Chapter 10 – Mechanical Properties of Fluids-Part 8

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Question 10.18:

Figure (a) shows a thin liquid film supporting a small weight. What is the weight supported by a film of the same liquid at the same temperature in Figure (b) and (c)?

Take case (a):

The length of the liquid film supported by the weight,

The weight supported by the film,

A liquid film has two free surfaces.

In all the three figures, the liquid is the same. Temperature is also the same for each case. Hence, the surface tension in figure (b) and figure (c) is the same as in figure (a), i.e.,

Since the length of the film in all the cases is 40 cm, the weight supported in each case is

Question 10.19:

What is the pressure inside the drop of mercury of radius at room temperature? Surface tension of mercury at that temperature . The atmospheric pressure is . Also give the excess pressure inside the drop.

Explanation: