11th assignment JEE NEET/PMT

Questions based on surface tension

This assignment contains some important questions based on the surface tension, in which there are some objective and some numericals based questions.

these questions are for the practice of the topic surface tension and surface energy, excess pressure inside the liquid drop, soap bubble , ascent formula etc.

Question based on surface tension and surface energy

Multiple choice questions. (Only one option is correct)

1. The angle of contact doesn’t depend upon,     (a)  Temperature         (b)Surface impurity      (c) Cohesive force      (d) The inclination of surface in contact.   Ans -d

2. When a capillary tube is immersed in a liquid , then the liquid of mass m rises in the capillary tube .If capillary tube of double radius is taken then the mass f same liquid rising in the tube is , ,     (a)   M/2        (b)   2M   (c) M/4     (d) 4M .                                                      Ans- b

3. What will be the work done to increasing the radius of the soap bubble from r/2 to 2r . If surface tension of soap solution is T ? ,     (a) 3πr2T   (b) 30πr2T    (c)    9πr2T   (d) 12πr2T   . Ans-b

4. pressure inside soap bubble are 1.02 atm and 1.05 atm respectively . then the ratio of their surface area is (a) 125/8 (b) 25/4  (c)5/2   (d)2/5.   Ans-b

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5.The property utilized in the manufacture of lead shots is (a)specific gravity of lead   (b)specific weight of the liquid lead  (c) compressibility of the liquid lead  (d) surface tension of the liquid lead. Ans-d

6. Two soap bubbles are connected by a tube as shown in figure , what happens when stopper s is removed ?

(a)size of A increase   (b) size of B is decreased   (c) both takes the same size (d) size of bubble A decreases and size of bubble B increases.                     Ans-d

7. Two soap bubble of radii 2cm and 4 cm are join to form a double bubble in air , then the radius of curvature of the interface is , (a)2√5 cm  (b)2cm  (c)4  cm (d)  2√3cm  .  Ans-c

8. A square wire frame of  side l is floating on the surface of the liquid of surface tension T . The force required to pull out the frame from the liquid is  (a) Tl  (b) 2Tl  (c) 4Tl  (d) 8Tl . Ans-d

9. Two drops of liquid coalesce to form a single drop . In this process energy is (a) Absorbed  (b) Evolved  (c) Either absorbed or evolved    (d) Neither absorbed nor evolved.  Ans-b

10. Surface tension of a liquid , at critical temperature is (a)Maximum   (b)Unchanged  (c)  Zero (d) none of these.                                                                                                           Ans-c

Important numericals based on this topic –


1.The surface tension of the soap solution is 30 x 10-3N/m .How much work is done to increase the radius of the soap bubble from 1.5 cm to 3 cm .     Ans- 5.091 x 10-4 j.

2. A square glass plate of length 10cm and thickness 0.4cm, weighs 40 g in air . It is held vertically such that its lower edge rests on water surface. What is the apparent weight of glass plate now? (S.T. of water is 0.073 N/m).                                                     Ans-0.407N.

3. The radii of two air bubbles are in the ratio 4:5 .Find the ratio of excess pressure inside them . Also compare the works done in Blowing these bubbles.             Ans-5/4  ; 16/25 . .

4. A circular plate of radius 4cm and weight W is made to rest on the surface of water if a minimum pull of   W+F is required to clear the plate off the water surface then find F , given surface tension of water is 0.072N/M.                       Ans-0.018N .

5. Water rises up in a glass capillary upto a height of 10cm , while mercury falls down by 3.5 cm in the same tube. If the angle of contact for water – glass and mercury-glass are is taken as 00 and 1350 respectively . compare the surface tension of water and mercury. [ density of water and mercury are 103 and 13.6×103kg/m3.].

6. A canister has a small hole at its bottom .What penetrates into the canister when its base is at a depth of 40cm from the surface of water. If surface tension of water is 73.5 dyne/cm, find the radius of the hole .     Ans- 0.0375mm.

To get the solution of all numerical questions given above click here

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