11th assignment Assignments

Important questions of mechanical properties of fluid in rest

Important questions of mechanical properties of fluid in rest (Hydrostatics);

This assignment contain all important questions based on the topic , liquid pressure, Pascal’s law, surface tension etc. It will help the students to prepare for the schools examination for class 11th.

1. Define thrust  and derive an expression for the pressure at depth in a liquid at rest under gravity.

2. State and prove Pascal’s law . Describe the principle and working of hydraulic press, or hydraulic lift.

3. What do you mean by up-thrust force? explain.  Obtain the conditions for floating and equilibrium of a floating body.

4. Describe briefly Torricelli’s experiment. What do you understand by the statement that the atmospheric pressure in 76cm of Hg column.

5. Define surface tension and surface energy show that surface energy is equivalent to surface tension.

6. Define angle of contact . How can it be determined  in case of mercury and glass?

7. Derive an expression for the excess pressure inside (i) a liquid drop and (ii) a soap bubble (iii) an air bubble in liquid .

To watch the video on the topic excess pressure inside liquid drop and soap bubble click here-

8. What is capillarity? Explain the capillary rise in liquid , deduce an expression for the rise .

9. Explain why

(a) The angle of contact of mercury with glass is obtuse , while that of water with glass is acute.

(b) Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops .

(c) Surface tension of a liquid is independent of the area of the surface .

(d)Water with detergent is dissolved in it should have small angles of contact .

(e) A drop of liquid under no external force is always spherical in shape .

(f) To keep a piece of paper horizontal. You should blow over not under it.

(g)A spinning cricket ball in air doesn’t follow a parabolic trajectory.


1. A 50 kg girls wearing high heel shoes balance on a single heel . The heel is circular with a diameter 1.0cm . What is the pressure exerted by the heel on the horizontal floor?    Ans-6.2x 106N/m2.

2. What is the pressure inside the drop of mercury of radius 3mm at room temperature? T for mercury is 4.56×10-1n/m also give the excess pressure inside the drop. Ans-310pa,1,01×105N/m2.

3. A U-shaped wire is dipped in the soap solution, and removed . The thin soap film formed between the wire and the light slider support a weight of 1.5×10-2N . The length of the slider is 30cm. What is the surface tension of the film?     Ans-2.5×10-2N/m.