Practice Test


1) Estimate the pressure difference between the lower and upper surfaces of the wings.


2) What is the pressure difference between the two ends of the tube?


3) What is the Reynolds number?


4) The equation of continuity. Which is valid for incompressible fluids is a statement of


5) The Bernoulli's equation that is valid for nor-viscous, incompressible fluids having laminar flow is a consequence of


6) Magnus effect is the


7) The dimensions of viscosity are


8) The Reynold's number equals


9) The surface energy of a liquid drop of radius r is proportional to


10) In a satellite moving around any planet, the gravitational force is effectively balanced. If the ice cube exists there, and it melts with passage of time, its shape will


11) A liquid is contained in a vessel. The liquid solid adhesive force is very weak as compared to the cohesive force in the liquid. The shape of the liquid surface will be


12) Two liquids drops coalesce to form a large drop. Now,


13) Statement 1 : The viscosity of a liquid increases with rise of temperature.
Statement 2: Viscosity of liquid is the property of the liquid by virtue of which it opposes the relative motion amongst its different layers.


14) Statement 1 : Two row boats moving parallel to each other and nearby, are attracted towards each other.
Statement 2 : Increase of velocity of fluid flow decreases the pressure between them.


15) The correct diagram showing the trajectories is


16) When two capillary tubes of different diameters are dipped vertically, the rise of the liquid is


17) The term 'surface of a liquid' means


18) If ice melts under gravity free conditions in vacuum, the final geometrical shape will be


19) The excess pressure due to surface tension inside a spherical drop in 6 units. If eight such drops combine, then the excess pressure due to surface tension inside the larger drop is


20) What is the ratio of excess pressures inside two soap bubbles of diameters in the ratio 2 : 1?


21) The surface energy of a liquid drop is E. It is sprayed into 1000 equal droplets. Then its surface energy becomes


22) The pressure energy per unit volume of a liquid is


23) A water tank of height 10 m, completely filled with water is placed on a level ground. It has two holes one at 3 m and the other at 7 m from its base. The water ejecting from


24) The vertical sections of the wing of a fan are shown in figure. Maximum upthrust is in


25) The work done by the force of gravity per unit volume is


26) Statement 1 : When two soap bubbles having different radii are kept in contact, the common surface at their interface bulges into the larger bubble.
Statement 2: Pressure inside the smaller bubble is larger.


27) Statement 1 : All the rain drops do not reach the surface of the earth with the same velocity.
Statement 2 : An object falling through a viscous medium eventually attains a terminal velocity.


28) What is the work done by surface tension force?


29) What is the rise in the potential energy of the liquid?


30) What is the work done against friction of the capillary. (Assume liquid rises slowly in the tube)


31) The value of surface tension of a liquid at critical temperature is


32) The spherical shape of rain-drop is due to


33) Surface tension is due to


34) When there is no external force, the shape of a liquid drop is determined by


35) Soap helps in cleaning clothes, because


36) A pin or a needle floats on the surface of water, the reason for this is


37) Coatings used on raincoat are waterproof because


38) If temperature increases, the surface tension of a liquid


39) A drop of oil is placed on the surface of water. Which of the following statement is correct


40) The temperature at which the surface tension of water is zero


41) A small air bubble is at the inner surface of the bottom of a beaker filled with cold water. Now water of the beaker is heated. The size of bubble increases. The reason for this may be


42) The spiders and insects move and run about on the surface of water without sinking because


43) Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid because


44) Hairs of shaving brush cling together when it is removed from water due to


45) A square frame of side L is dipped in a liquid. On taking out, a membrane is formed. If the surface tension of the liquid is T, the force acting on the frame will be


46) Water does not wet an oily glass because


47) A water drop takes the shape of a sphere in a oil while the oil drop spreads in water, because
(A.F. = adhesive force C.F. = cohesive force)


48) Which of the fact is not due to surface tension


49) In the glass capillary tube, the shape of the surface of the liquid depends upon


50) Force necessary to pull a circular plate of 5 cm radius from water surface for which surface tension is 75 dynes/cm, is


51) The property of surface tension is obtained in


52) The surface tension of a liquid


53) If two glass plates are quite nearer to each other in water, then there will be force of


54) On mixing the salt in water, the surface tension of water will


55) Consider a liquid contained in a vessel. The liquid solid adhesive force is very weak as compared to the cohesive force in the liquid. The shape of the liquid surface near the solid shall be


56) At which of the following temperatures, the value of surface tension of water is minimum


57) If a glass rod is dipped in mercury and withdrawn out, the mercury does not wet the rod because


58) Mercury does not wet glass, wood or iron because


59) Surface tension of a liquid is found to be influenced by


60) When a drop of water is dropped on oil surface, then


61) Two pieces of glass plate one upon the other with a little water in between them cannot be separated easily because of


62) Small liquid drops assume spherical shape because


63) It is easy to wash clothes in hot water because its


64) Due to which property of water, tiny particles of camphor dance on the surface of water


65) Oil spreads over the surface of water whereas water does not spread over the surface of the oil, due to


66) Cohesive force is experienced between


67) The property utilized in the manufacture of lead shots is


68) The dimensions of surface tension are


69) A wooden stick 2m long is floating on the surface of water. The surface tension of water 0.07 N/m. By putting soap solution on one side of the sticks the surface tension is reduced to 0.06 N/m. The net force on the stick will be


70) The force required to take away a flat circular plate of radius 2 cm from the surface of water, will be (the surface tension of water is 70 dyne/cm)


71) Surface tension may be defined as


72) Energy needed in breaking a drop of radius R into n drops of radii r is given by


73) The potential energy of a molecule on the surface of liquid compared to one inside the liquid is


74) Two droplets merge with each other and forms a large droplet. In this process


75) A drop of liquid of diameter 2.8 mm breaks up into 125 identical drops. The change in energy is nearly (S.T. of liquid =75 dynes/cm)


76) Radius of a soap bubble is 'r', surface tension of soap solution is T. Then without increasing the temperature, how much energy will be needed to double its radius


77) A spherical liquid drop of radius R is divided into eight equal droplets. If surface tension is T, then the work done in this process will be


78) The amount of work done in blowing a soap bubble such that its diameter increases from d to D is (T= surface tension of the solution)


79) If T is the surface tension of soap solution, the amount of work done in blowing a soap bubble from a diameter D to 2D is


80) If work W is done in blowing a bubble of radius R from a soap solution, then the work done in blowing a bubble of radius 2R from the same solution is


81) A spherical drop of oil of radius 1 cm is broken into 1000 droplets of equal radii. If the surface tension of oil is 50 dynes/cm, the work done is


82) The work done in blowing a soap bubble of radius r of the solution of surface tension T will be


83) If two identical mercury drops are combined to form a single drop, then its temperature will


84) If the surface tension of a liquid is T, the gain in surface energy for an increase in liquid surface by A is


85) The surface tension of a liquid at its boiling point


86) What is ratio of surface energy of 1 small drop and 1 large drop, if 1000 small drops combined to form 1 large drop


87) One thousand small water drops of equal radii combine to form a big drop. The ratio of final surface energy to the total initial surface energy is


88) A big drop of radius R is formed by 1000 small droplets of water, then the radius of small drop is


89) Which of the following statements are true in case when two water drops coalesce and make a bigger drop


90) 8000 identical water drops are combined to form a big drop. Then the ratio of the final surface energy to the initial surface energy of all the drops together is


91) 8 mercury drops coalesce to form one mercury drop, the energy changes by a factor of


92) When two small bubbles join to form a bigger one, energy is


93) Two small drops of mercury, each of radius R, coalesce to form a single large drop. The ratio of the total surface energies before and after the change is


94) Radius of a soap bubble is increased from R to 2R work done in this process in terms of surface tension is


95) The work done in blowing a soap bubble of radius 0.2 m is (the surface tension of soap solution being 0.06 N/m)


96) If two soap bubbles of equal radii r coalesce then the radius of curvature of interface between two bubbles will be


97) A liquid does not wet the sides of a solid, if the angle of contact is


98) The meniscus of mercury in the capillary tube is


99) When the temperature is increased the angle of contact of a liquid


100) The angle of contact between glass and mercury is


101) A mercury drop does not spread on a glass plate because the angle of contact between glass and mercury is


102) A liquid is coming out from a vertical tube. The relation between the weight of the drop W, surface tension of the liquid T and radius of the tube r is given by, if the angle of contact is zero


103) The parts of motor cars are polished by chromium because the angle of contact between water and chromium is


104) A glass plate is partly dipped vertically in the mercury and the angle of contact is measured. If the plate is inclined, then the angle of contact will


105) The liquid meniscus in capillary tube will be convex, if the angle of contact is


106) If a water drop is kept between two glass plates, then its shape is


107) The value of contact angle for kerosene with solid surface.


108) A liquid wets a solid completely. The meniscus of the liquid in a sufficiently long tube is


109) What is the shape when a non-wetting liquid is placed in a capillary tube


110) What is the shape when a non-wetting liquid is placed in a capillary tube


111) For which of the two pairs, the angle of contact is same


112) If the surface of a liquid is plane, then the angle of contact of the liquid with the walls of container is


113) A soap bubble assumes a spherical surface. Which of the following statement is wrong


114) If two soap bubbles of different radii are in communication with each other


115) The excess pressure due to surface tension in a spherical liquid drop of radius r is directly proportional to


116) A long cylindrical glass vessel has a small hole of radius 'r' at its bottom. The depth to which the vessel can be lowered vertically in the deep water bath (surface tension T) without any water entering inside is


117) If the surface tension of a soap solution is 0.03 MKS units, then the excess of pressure inside a soap bubble of diameter 6 mm over the atmospheric pressure will be


118) The excess of pressure inside a soap bubble than that of the outer pressure is


119) The pressure of air in a soap bubble of 0.7cm diameter is 8 mm of water above the pressure outside. The surface tension of the soap solution is


120) Pressure inside two soap bubbles are 1.01 and 1.02 atmospheres. Ratio between their volumes is


121) When a large bubble rises from the bottom of a lake to the surface, its radius doubles. If atmospheric pressure is equal to that of column of water height H, then the depth of lake is


122) A soap bubble in vacuum has a radius of 3 cm and another soap bubble in vacuum has a radius of 4 cm. If the two bubbles coalesce under isothermal condition, then the radius of the new bubble is


123) The volume of an air bubble becomes three times as it rises from the bottom of a lake to its surface. Assuming atmospheric pressure to be 75 cm of Hg and the density of water to be 1/10 of the density of mercury, the depth of the lake is


124) Excess pressure of one soap bubble is four times more than the other. Then the ratio of volume of first bubble to another one is


125) There are two liquid drops of different radii. The excess pressure inside over the outside is


126) If pressure at half the depth of a lake is equal to 2/3 pressure at the bottom of the lake then what is the depth of the lake


127) If the radius of a soap bubble is four times that of another, then the ratio of their pressures will be


128) The pressure at the bottom of a tank containing a liquid does not depend on


129) In capillary pressure below the curved surface of water will be


130) Two bubbles A and B are (A > B) joined through a narrow tube. Then


131) Two soap bubbles have different radii but their surface tension is the same. Mark the correct statement


132) If the excess pressure inside a soap bubble is balanced by oil column of height 2 mm, then the surface tension of soap solution will be (r = 1 cm and density d = 0.8 gm/cc)


133) In Jager's method, at the time of bursting of the bubble


134) The excess pressure in a soap bubble is thrice that in other one. Then the ratio of their volume is


135) When two capillary tubes of different diameters are dipped vertically, the rise of the liquid is


136) Due to capillary action, a liquid will rise in a tube, if the angle of contact is


137) In the state of weightlessness, a capillary tube is dipped in water, then water


138) Two parallel glass plates are dipped partly in the liquid of density 'd' keeping them vertical. If the distance between the plates is 'x', surface tension for liquids is T and angle of contact is , then rise of liquid between the plates due to capillary will be


139) It is not possible to write directly on blotting paper or newspaper with ink pen


140) Two capillary tubes P and Q are dipped in water. The height of water level in capillary P is 2/3 to the height in Q capillary. The ratio of their diameters


141) Two capillaries made of same material but of different radii are dipped in a liquid. The rise of liquid in one capillary is 2.2 cm and that in the other is 6.6 cm. The ratio of their radii is


142) When a capillary is dipped in water, the water rises to a height h. If the length of the capillary is made less than h, then


143) Water rises upto 10 cm height in a long capillary tube. If this tube is immersed in water so that the height above the water surface is only 8 cm, then


144) A capillary tube made of glass is dipped into mercury. Then


145) By inserting a capillary tube upto a depth l in water, the water rises to a height h. If the lower end of the capillary is closed inside water and the capillary is taken out and closed end opened, to what height the water will remain in the tube


146) If the diameter of a capillary tube is doubled, then the height of the liquid that will rise is


147) Two capillary tubes of radii 0.2 cm and 0.4 cm are dipped in the same liquid. The ratio of heights through which liquid will rise in the tubes is


148) The action of a nib split at the top is explained by


149) The correct relation is


150) Water rises upto a height h in a capillary on the surface of earth in stationary condition. Value of h increases if this tube is taken


151) During capillary rise of a liquid in a capillary tube, the surface of contact that remains constant is of


152) A shell having a hole of radius r is dipped in water. It holds the water upto a depth of h then the value of r is


153) In a capillary tube, water rises by 1.2 mm. The height of water that will rise in another capillary tube having half the radius of the first, is


154) If capillary experiment is performed in vacuum then for a liquid there


155) If liquid level falls in a capillary then radius of capillary will


156) Water rises to a height h in a capillary at the surface of earth. On the surface of the moon the height of water column in the same capillary will be


157) The surface tension for pure water in a capillary tube experiment is


158) In a capillary tube experiment, a vertical 30 cm long capillary tube is dipped in water. The water rises up to a height of 10cm due to capillary action. If this experiment is conducted in a freely falling elevator, the length of the water column becomes


159) In a capillary tube, water rises to 3 mm. The height of water that will rise in another capillary tube having one-third radius of the first is


160) Kerosene oil rises up the wick in a lantern


161) Water rises against gravity in a capillary tube when its one end is dipped into water because


162) A capillary tube of radius R is immersed in water and water rises in it to a height H. Mass of water in the capillary tube is M. If the radius of the tube is doubled, mass of water that will rise in the capillary tube will now be


163) Water rises up to a height h in a capillary tube of certain diameter. This capillary tube is replaced by a similar tube of half the diameter. Now the water will rise to the height of


164) There is a horizontal film of soap solution. On it a thread is placed in the form of a loop. The film is pierced inside the loop and the thread becomes a circular loop of radius R. If the surface tension of the loop be T, then what will be the tension in the thread


165) A large number of water drops each of radius r combine to have a drop of radius R. If the surface tension is T and the mechanical equivalent of heat is J, then the rise in temperature will be


166) An air bubble in a water tank rises from the bottom to the top. Which of the following statements are true


167) In a surface tension experiment with a capillary tube water rises upto 0.1 m. If the same experiment is repeated on an artificial satellite, which is revolving around the earth, water will rise in the capillary tube upto a height of


168) The correct curve between the height or depression h of liquid in a capillary tube and its radius is


169) A soap bubble is blown with the help of a mechanical pump at the mouth of a tube. The pump produces a certain increase per minute in the volume of the bubble, irrespective of its internal pressure. The graph between the pressure inside the soap bubble and time t will be-


170) Which graph represents the variation of surface tension with temperature over small temperature ranges for water


171) Assertion :
It is easier to spray water in which some soap is dissolved.
Reason :
Soap is easier to spread.


172) Assertion :
It is better to wash the clothes in cold soap solution.
Reason :
The surface tension of cold solution is more than the surface tension of hot solution.


173) Assertion : When height of a tube is less than liquid rise in the capillary tube, the liquid does not overflow.
Reason :
Product of radius of meniscus and height of liquid in capillary tube always remains constant.


174) Assertion :
A needle placed carefully on the surface of water may float, whereas a ball of the same material will always sink.
Reason :
The buoyancy of an object depends both on the material and shape of the object.


175) Assertion :
A large force is required to draw apart normally two glass plates enclosing a thin water film.
Reason :
Water works as glue and sticks two glass plates.


176) Assertion :
The impurities always decrease the surface tension of a liquid.
Reason :
The change in surface tension of the liquid depends upon the degree of contamination of the impurity.


177) Assertion :
The angle of contact of a liquid decrease with increase in temperature.
Reason :
With increase in temperature, the surface tension of liquid increase.


178) Assertion :
The concept of surface tension is held only for liquids.
Reason :
Surface tension does not hold for gases.


179) Assertion :
At critical temperature, surface tension of a liquid becomes zero.
Reason :
At this temperature, intermolecular forces for liquids and gases become equal. Liquid can expand without any restriction.


180) Assertion :
A large soap bubble expands while a small bubble shrinks, when they are connected to each other by a capillary tube.
Reason :
The excess pressure inside bubble (or drop) is inversely proportional to the radius.


181) Assertion :
Tiny drops of liquid resist deforming forces better than bigger drops.
Reason :
Excess pressure inside a drop is directly proportional to surface tension.


182) Assertion :
The water rises higher in a capillary tube of small diameter than in the capillary tube of large diameter.
Reason :
Height through which liquid rises in a capillary tube is inversely proportional to the diameter of the capillary tube.


183) Assertion :
Hot soup tastes better than the cold soup.
Reason :
Hot soup has high surface tension and it does not spread properly on our tongue.


184) Assertion :
The shape of a liquid drop is spherical.
Reason :
The pressure inside the drop is greater than that of outside.


185) Energy required to form a soap bubble of diameter 20 cm will be (Surface tension for soap solution is 30 dynes/cm)


186) If the work done in blowing a bubble of volume V is W, then the work done in blowing the bubble of volume 2V from the same soap solution will be


187) Excess pressure inside a soap bubble is three times that of the other bubble, then the ratio of their volumes will be


188) When a capillary tube is dipped in water it rises upto 8 cm in the tube. What happens when the tube is pushed down such that its end is only 5 cm above the outside water level


189) A bubble of 8 mm diameter is formed in the air. The surface tension of soap solution is 30 dynes/cm. The excess pressure inside the bubble is


190) The height upto which water will rise in a capillary tube will be


191) A drop of water breaks into two droplets of equal size. In this process, which of the following statement is correct


192) A soap bubble of radius R is blown. After heating the solution a second bubble of radius 2R is blown. The work required to blow the second bubble in comparison to that required for the first bubble is


193) A false statement is


194) Water rises to a height of 16.3 cm in a capillary of height 18 cm above the water level. If the tube is cut at a height of 12 cm