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# Important numericals of surface tension

This assignment contains Important numericals of surface tension which is solved . solution is given just below the questions.

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.

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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 .

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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.

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