Two separate air bubbles (radii 0.002 m and 0.004 m) formed of the same liquid (surface tension 0.07 N/m) come together to form a double bubble. Find the radius and the sense of curvature of the internal film surface common to both the bubbles. 


Correct option is

0.004 m


If r1 and r2 are the radii of smaller and larger bubbles and p0 is the atmospheric pressure, the pressure inside them will be


Now as the pressure inside the smaller bubble will be more than inside the larger bubble, so for interface,


Now as excess pressure acts form concave to convex side, the interface will be concave towards smaller bubble and convex towards larger bubble (as shown in figure) and if R is the radius of interface,                      



So substituting eq. (i) and (iii) in (ii), we get 


So here 




A spherical ball of radius  and 104 kg/m3 falls freely under gravity through a distance h before entering a tank of water. If after entering the water the velocity of the ball does not change, find h. The viscosity of water is .


Water flows through a capillary tube of radius r and length l at a rate of 40 ml per second, when connected to a pressure difference of h cm of water. Another tube of the same length but radius r/2 is connected in series with this tube and the combination is connected to the same pressure head. Calculate the pressure difference across each tube and the rate of flow of water through the combination.  



Spherical particles of pollen are shaken up in water and allowed to settle. The depth of the water is . What is the diameter of largest particles remaining in suspension on hour later?



A cylindrical vessel of area of cross-section and filled with liquid to a height of h1 has a capillary tube of length 1 and radius r protruding horizontally at its bottom. If the viscosity of liquid is , density  and g = 9.8 m/s2, find the time in which the level of water in vessel falls to h2.


Vessel whose bottom has round holes with diameter of 1 mm is filled with water. Assuming that surface tension acts only at holes, find the maximum height to which the water can filled in the vessel without leakage. Given that surface tension of water is 


A ring is cut from a platinum tube of 8.5 cm internal and 8.7 cm external diameter. It is supported horizontally from a pan of a balance so that it comes in contact with the water in a glass vessel. What is the surface tension of water is an extra 3.97 g weight is required to pull it away from water? (g = 980 cm/s2)



A mercury drop of radius 1 cm is sprayed into 106 droplets of equal size. Calculate the energy expended if surface tension of mercury* is .


The lower end of a capillary tube of diameter 2.00 mm is dipped 8.00 cm below the surface of water in a beaker. What is the pressure required in the tube to blow a bubble at its end in water? Also calculate the excess pressure. [Surface tension of water  density of water = 103kg/m3, 1 atmosphere 


The limbs of a manometer consist of uniform capillary tubes of radii . Find out the correct pressure difference if the level of the liquid (density 103 kg/m3, surface tension ) in narrower tube stands 0.2 m above that in the broader tube. 


A glass capillary sealed at the upper end is of length 0.11 m and internal diameter . The tube is immersed vertically into a liquid of surface tension . To what length has the capillary to be immersed so that the liquid level inside and outside the capillary becomes the same? What will happen to the water level inside the capillary if the seal is now broken?