Question 4 :
The surface tension of soap solution is $0.03 {N}/{m}$. The work done in blowing to from a soap bubble of surface area $40{ cm }^{ 2 }$, (in $J$), is
Question 5 :
The lower end of a capillary tube of radius r is placed vertically in water. With the rise h of water in the capillary tube, evolved is (Take p as the density of water)
Question 6 :
A metal sphere of diameter $7 cm$ falls through a liquid of coefficient of viscosity $0.8 Pa.s$. When its velocity is $20 cm.s^{-1}$ the viscous force acting on it is nearly ----$N.$
Question 8 :
Water if flowing steadily through a horizontal pipe of non-uniform cross-section. If the velocity of water at a point where cross-section is $0.02 m^3$ is $2m/s$, what is the velocity of water at another point where the cross-section is $0.01 m^3$ ?
Question 9 :
Assertion: A small drop of mercury is spherical but bigger drops are oval in shape.
Reason: Surface tension of liquid decreases with increase in temperature.
Question 10 :
For which of the following options, surface tension is not the basis ?
Question 11 :
A piston of cross-sectional area $100\ cm^{2}$ is used in a hydraulic press to exert a force of $10^{7}$ dyne on the water. The cross sectional area of the other piston which supports an object having a mass of $2000\ kg$ is
Question 12 :
A small metal ball of diameter $4\ mm$ and density $10.5\ g/cm^{3}$ in dropped in glycerine of density $1.5\ g/cm^{3}$. The ball attains a terminal velocity of $8\ cm/\sec$. The coefficient of viscosity of glycerine is
Question 13 :
A liquid is flowing in a horizontal uniform capillary tube under a constant pressure difference p. The value of pressure for which the rate of flow of the liquid is doubled when the radius and length both are doubled, is
Question 14 :
A small steel ball falls through a syrup at a constant speed of 10 m/s. If the steel ball is pulled upwards with a force equal to twice its effective weight, how fast will it move upwards?
Question 15 :
In which one of the following cases will the liquid flow in a pipe be most streamlined
Question 16 :
A solid sphere falls with a terminal velocity of 10 m/s in air. If it is allowed to fall in vacuum:<br/>
Question 17 :
Air is streaming past a horizontal airplane wing such that its speed is $90 ms^{-1}$ at the lower surface and $120 ms^{-1}$ over the upper surface. If the wing is 10 m long and has an average width of 2m, the difference of pressure on the two sides and the gross lift on the wing respectively, are (density of air $=1.3 kg m^{-3})$<br>