MEDIUM
JEE Advanced
IMPORTANT
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A soap bubble is being blown on a tube of radius 1 cm. The surface tension of the soap solution is 0.05Nm-1 and the bubble makes 60° with the tube as shown in the figure. Find the excess of pressure over the atmosphere pressure in the tube (in Pa )

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Important Questions on Surface Tension and Viscosity

HARD
JEE Advanced
IMPORTANT
A bowl whose bottom has round holes of diameter 1 mm is filled with water. Assuming that surface tension acts only at holes, find the maximum height (in cm ) up to which water can be filled in the vessel without leakage. (Given, surface tension of water =75×10-3 N m-1, g=10 m s-2 and density of water =1000 kg m-3 ).
HARD
JEE Advanced
IMPORTANT

A soap film is made by dropping a circular frame of radius b in soap solution. A bubble is formed by blowing air with speed v in the form of a cylinder. Air stops after striking surface of soap bubble. Density of air is ρ. The radius of the bubble is R>b. The radius R of the bubble when the soap bubble separates from the ring is βTρv2. Find the value of β. (where, surface tension of liquid is T ).

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MEDIUM
JEE Advanced
IMPORTANT
A metallic sphere of radius 1.0×10-3 m and density 10×104 kg/m3 enters a tank of water, after a free fall through a distance of h in the earth's gravitational field. If its velocity remains unchanged after entering water, determine the value of h (in m ). Given: coefficient of viscosity of water =1.0×10-3 N-s/m2,g=10 m/s2 and density of water =1.0×103 kg/m3
MEDIUM
JEE Advanced
IMPORTANT
A small steel ball falls through a syrup at a constant speed of 10 cm s-1. If the steel ball is pulled upwards with a force equal to twice its effective weight, find the terminal velocity of the ball (in cm/s ) in this case.
HARD
JEE Advanced
IMPORTANT

A circular ring has inner and outer radii equal to 20 mm and 50 mm respectively. Mass of the ring is m=0.8 g. It gently pulled out vertically from a water surface by a sensitive spring. When the spring is stretched 4 cm from its equilibrium position the ring is on verge of being pulled out from the water surface. If spring constant is k=0.9 N m-1 and g=10 m s-2, the surface tension of water(in N m-1) is x×10-3. Write the value of x, where   is the greatest integer function.

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MEDIUM
JEE Advanced
IMPORTANT

A long thin walled capillary tube of mass M=10 g and radius r=7 mm is partially immersed in a liquid of surface tension T=0.75 N m-1. The angle of contact for the liquid and the tube wall is 60°. How much force(in N) is needed to hold the tube vertically? Neglect buoyancy force on the tube.

(Take g=10 m s-2, π=227)

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MEDIUM
JEE Advanced
IMPORTANT
A tapering glass capillary tube A of length 0.1 m has diameters 10-3 m and 5×10-4 m at the ends. When it is just immersed in a liquid at 0°C with larger radius in contact with liquid surface, the liquid rises 8×10-2 m in the tube. In another experiment, in a cylindrical glass capillary tube B, when immersed in the same liquid at 0°C, the liquid rises to 6×10-2 m height. The rise of liquid in tube B is only 5.5× 10-2 m when the liquid is at 50°C. Find the rate at which the surface tension changes (in ×10-4 N/mC ) with temperature considering the change to be linear. The density of liquid is (1/14)×104 kg/m3 and the angle of contact is zero. Effect of temperature on the density of liquid and glass is negligible.
MEDIUM
JEE Advanced
IMPORTANT
There is an air bubble of radius 1.0 mm in a liquid of surface tension 0.075 N/m and density 1000 kg/m3. The bubble is at a depth of 10 cm below the free surface. By what amount is the pressure (in Pa) inside the bubble greater than the atmospheric pressure? (Take g=9.8 m/s2 )