Practice Test

Q1) 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 Show Answer

Q2) Equal masses of water and a liquid of density 2 are mixed together, and then the mixture has a density of Show Answer

Q3) The pressure at the bottom of a tank containing a liquid does not depend on Show Answer

Q4) 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 Show Answer

Q5) 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 Show Answer

Q6) The value of g at a place decreases by 2%. The barometric height of mercury Show Answer

Q7) A barometer kept in a stationary elevator reads 76 cm. If the elevator starts accelerating up the reading will be Show Answer

Q8) A beaker containing a liquid is kept inside a big closed jar. If the air inside the jar is continuously pumped out, the pressure in the liquid near the bottom of the liquid will Show Answer

Q9) The height to which a cylindrical vessel be filled with a homogeneous liquid, to make the average force with which the liquid presses the side of the vessel equal to the force exerted by the liquid on the bottom of the vessel, is equal to Show Answer

Q10) With rise in temperature, density of a given body changes according to one of the following relations Show Answer

Q11) Three liquids of densities d, 2 d and 3 d are mixed in equal volumes. Then the density of the mixture is Show Answer

Q12) Why the dam of water reservoir is thick at the bottom? Show Answer

Q13) A concrete sphere of radius R has a cavity of radius r which is packed with sawdust. The specific gravities of concrete and sawdust are respectively 2.4 and 0.3 for this sphere to float with its entire volume submerged under water. Ratio of mass of concrete to mass of sawdust will be Show Answer

Q14) Two solids A and B float in water. It is observed that floats with half its volume immersed and B floats with 2/3 of its volume immersed. Compare the densities of A and B Show Answer

Q15) Pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel. This law was first formulated by Show Answer

Q16) A body is just floating on the surface of a liquid. The density of the body is same as that of the liquid. The body is slightly pushed down. What will happen to the body Show Answer

Q17) A cork is submerged in water by a spring attached to the bottom of a bowl. When the bowl is kept in an elevator moving with acceleration downwards, the length of spring Show Answer

Q18) A hollow sphere of volume V is floating on water surface with half immersed in it. What should be the minimum volume of water poured inside the sphere so that the sphere now sinks into the water? Show Answer

Q19) A boat carrying steel balls is floating on the surface of water in a tank. If the balls are thrown into the tank one by one, how will it affect the level of water Show Answer

Q20) Two pieces of metal when immersed in a liquid have equal up thrust on them; then Show Answer

Q21) A wooden cylinder floats vertically in water with half of its length immersed. The density of wood is Show Answer

Q22) An ice block contains a glass ball when the ice melts within the water containing vessel, the level of water Show Answer

Q23) A large ship can float but a steel needle sinks because of Show Answer

Q24) Construction of submarines is based on Show Answer

Q25) In which one of the following cases will the liquid flow in a pipe be most streamlined Show Answer

Q26) Two water pipes of diameters 2 cm and 4 cm are connected with the main supply line. The velocity of flow of water in the pipe of 2 cm diameter is Show Answer

Q27) Air is streaming past a horizontal air plane wing such that its speed in 120 m/s over the upper surface and 90 m/s at the lower surface. If the density of air is 1.3 kg per metre3 and the wing is 10 m long and has an average width of 2 m, then the difference of the pressure on the two sides of the wing of Show Answer

Q28) There is a hole of area A at the bottom of cylindrical vessel. Water is filled up to a height h and water flows out in t second. If water is filled to a height 4h, it will flow out in time equal to Show Answer

Q29) A square plate of 0.1 m side moves parallel to a second plate with a velocity of 0.1 m/s, both plates being immersed in water. If the viscous force is 0.002 N and the coefficient of viscosity is 0.01 poise, distance between the plates in m is Show Answer

Q30) Two drops of the same radius are falling through air with a steady velocity of 5 cm per sec. If the two drops coalesce, the terminal velocity would be Show Answer

Q31) The rate of steady volume flow of water through a capillary tube of length 'l' and radius 'r' under a pressure difference of P is V. This tube is connected with another tube of the same length but half the radius in series. Then the rate of steady volume flow through them is (The pressure difference across the combination is P) Show Answer

Q32) 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 Show Answer

Q33) In a laminar flow the velocity of the liquid in contact with the walls of the tube is Show Answer

Q34) In a turbulent flow, the velocity of the liquid molecules in contact with the walls of the tube is Show Answer

Q35) Water is flowing through a tube of non-uniform cross-section ratio of the radius at entry and exit end of the pipe is 3 : 2. Then the ratio of velocities at entry and exit of liquid is Show Answer

Q36) Water is flowing through a horizontal pipe of non-uniform cross-section. At the extreme narrow portion of the pipe, the water will have Show Answer

Q37) In a streamline flow Show Answer

Q38) An application of Bernoulli's equation for fluid flow is found in Show Answer

Q39) The Working of an atomizer depends upon Show Answer

Q40) The pans of a physical balance are in equilibrium. Air is blown under the right hand pan; then the right hand pan will Show Answer

Q41) At what speed the velocity head of a stream of water be equal to 40 cm of Hg Show Answer

Q42) The weight of an aeroplane flying in air is balanced by Show Answer

Q43) A rectangular vessel when full of water takes 10 minutes to be emptied through an orifice in its bottom. How much time will it take to be emptied when half filled with water? Show Answer

Q44) The coefficient of viscosity for hot air is Show Answer

Q45) A small drop of water falls from rest through a large height h in air; the final velocity is Show Answer

Q46) In Poiseuilli's method of determination of coefficient of viscosity, the physical quantity that requires greater accuracy in measurement is Show Answer

Q47) Two capillaries of same length and radii in the ratio 1 : 2 are connected in series. A liquid flows through them in streamlined condition. If the pressure across the two extreme ends of the combination is 1 m of water, the pressure difference across first capillary is Show Answer

Q48) Water flows in a streamlined manner through a capillary tube of radius a, the pressure difference being P and the rate of flow Q. If the radius is reduced to a/2 and the pressure increased to 2P, the rate of flow becomes Show Answer

Q49) Water is flowing in a pipe of diameter 4 cm with a velocity 3 m/s. The water then enters into a tube of diameter 2 cm. The velocity of water in the other pipe is Show Answer

Q50) Water falls from a tap, down the streamline Show Answer

Q51) A large open tank has two holes in the wall. One is a square hole of side L at a depth y from the top and the other is a circular hole of radius R at a depth 4y from the top. When the tank is completely filled with water the quantities of water flowing out per second from both the holes are the same. Then R is equal to Show Answer

Q52) A block of ice floats on a liquid of density 1.2in a beaker then level of liquid when ice completely melts Show Answer

Q53) A lead shot of 1mm diameter falls through a long column of glycerine. The variation of its velocity v. with distance covered is represented by Show Answer

Q54) From amongst the following curves, which one shows the variation of the velocity v with time t for a small sized spherical body falling vertically in a long column of a viscous liquid Show Answer

Q55) Assertion : Pascal law is the working principle of a hydraulic lift.
Reason : Pressure is equal to thrust per area. Show Answer

Q56) Assertion : The blood pressure in humans is greater at the feet than at the brain.
Reason : Pressure of liquid at any point is proportional to height, density of liquid and acceleration due to gravity.
Show Answer

Q57) Assertion : Hydrostatic pressure is a vector quantity.
Reason : Pressure is force divided by area, and force is a vector quantity.
Show Answer

Q58) Assertion : To float, a body must displace liquid whose weight is greater than the actual weight of the body.
Reason :The body will experiences no net downward force, in the case of floating.
Show Answer

Q59) Assertion : A man sitting in a boat which is floating on a pond. If the man drinks some water from the pond, the level of the water in the pond decreases.
Reason : According to Archimede's principle the weight displaced by body is equal to the weight of the body. Show Answer

Q60) Assertion : A piece of ice floats in water, the level of water remains unchanged when the ice melts completely.
Reason : According to Archimede's principle, the loss in weight of the body in the liquid is equal to the weight of the liquid displaced by the immersed part of the body. Show Answer

Q61) Assertion : The velocity increases, when water flowing in broader pipe enter a narrow pipe.
Reason : According to equation of continuity, product of area and velocity is constant. Show Answer

Q62) In a stream line flow of a liquid, according to equation of continuity constant.
Where a is the area of cross section and v is the velocity of liquid flow. When water flowing in a broader pipe enters a narrow pipe, the area of cross-section of water decreases therefore the velocity of water increases. Show Answer

Q63) Assertion : The velocity of flow of a liquid is smaller when pressure is larger and vice-versa.
Reason : According to Bernoulli's theorem, for the stream line flow of an ideal liquid, the total energy per unit mass remains constant. Show Answer

Q64) Assertion : The shape of an automobile is so designed that its front resembles the stream line pattern of the fluid through which it moves.
Reason : The resistance offered by the fluid is maximum. Show Answer

Q65) Assertion : The size of the needle of a syninge controls flow rate better than the thumb pressure exerted by a doctor while administering an injection.
Reason : Flow rate is independent of pressure exerted by the thumb of the doctor. Show Answer

Q66) Assertion : A fluid flowing out of a small hole in a vessel apply a backward thrust on the vessel.
Reason : According to equation of continuity, the product of area and velocity remain constant. Show Answer

Q67) Assertion : For a floating body to be in stable equilibrium, its centre of buoyancy must be located above the centre of gravity.
Reason : The torque produced by the weight of the body and the up thrust will restore body back to its normal position, after the body is disturbed. Show Answer

Q68) Assertion : Water flows faster than honey.
Reason : The coefficient of viscosity of water is less than honey. Show Answer

Q69) Assertion : The viscosity of liquid increases rapidly with rise of temperature.
Reason : Viscosity of a liquid is the property of the liquid by virtue of which it opposes the relative motion amongst its different layers. Show Answer

Q70) Assertion : Aeroplanes are made to run on the runway before take off, so that they acquire the necessary lift.
Reason : According to Bernoulli's theorem, as velocity increases pressure decreases and vice-versa. Show Answer

Q71) Assertion : Sudden fall of pressure at a place indicates strom.
Reason : Air flows from higher pressure to lower pressure. Show Answer

Q72) Assertion : Machine parts are jammed in winter.
Reason :The viscosity of lubricant used in machine parts increase at low temperature. Show Answer

Q73) Assertion : A block of wood is floating in a tank containing water. The apparent weight of the floating block is equal to zero.
Reason : Because the entire weight of the block is supported by the buoyant force (the upward thrust) due to water. Show Answer

Q74) Assertion : A rain drop after falling through some height attains a constant velocity.
Reason : At constant velocity, the viscous drag is just equal to its weight. Show Answer

Q75) Assertion : Paper pins are made to have pointed end.
Reason : Because pointed pins have very small area due to which even for small applied force it exert large pressure on the surface. Show Answer

Q76) Assertion : Railways tracks are laid on small sized wooden sleepers.
Reason : Small sized wooden sleepers are used so that rails exert more pressure on the railway track. Due to which rail does not leave the track. Show Answer

Q77) Assertion : It is difficult to stop bleeding from a cut in the body at high altitudes.
Reason :The atmospheric pressure at high altitude is lesser than the blood pressure. Show Answer

Q78) Assertion : To empty an oil tank, two holes are made.
Reason : Oil will come out two holes so it will emptied faster. Show Answer

Q79) Assertion : Terminal velocity is same as the critical velocity.
Reason : The constant velocity of fall of a body through a viscous fluid is called terminal velocity. Show Answer

Q80) Assertion : When two boats sails parallel in the same direction and close to each other, they are pulled towards each other.
Reason : The viscous drag on a spherical body moving with speed v is proportional to v. Show Answer

Q81) Assertion : Cars and aeroplanes are streamlined.
Reason : This is done to reduce the backward drag due to atmosphere. Show Answer

Q82) A capillary tube is attached horizontally to a constant head arrangement. If the radius of the capillary tube is increased by 10% then the rate of flow of liquid will change nearly by Show Answer

Q83) Which of the following is not the characteristic of turbulent flow? Show Answer

Q84) The relative velocity of two consecutive layers is 8 cm/s. If the perpendicular distance between the layers is 0.1 cm, then the velocity gradient will be Show Answer

Q85) Under a constant pressure head, the rate of flow of liquid through a capillary tube is V. If the length of the capillary is doubled and the diameter of the bore is halved, the rate of flow would become Show Answer

Q86) Atmospheric pressure is measured by a Show Answer

Q87) Which one of the following is based on 'Pascal's Law'? Show Answer

Q88) 1 torr is the hydrostatic pressure exerted by a mercury column of height. Show Answer

Q89) Which one of the following is not a unit of pressure? Show Answer

Q90) The hydrostatic pressure exerted by a liquid does not depend upon the Show Answer

Q91) Pascal's law is not applied in Show Answer

Q92) By sucking through a straw, a student can reduce the pressure in his lungs from 760 mm to 750 mm of mercury. Using the straw, he can drink water from a glass upto a maximum depth of Show Answer

Q93) A cylindrical vessel is filled with mercury and water of equal weights. The total height of the two liquid layers is 29.2 cm. If the specific gravity of mercury is 13.6, then the height of mercury column will be Show Answer

Q94) The manual of a truck instructs the driver to inflate the tyres to a pressure of 210 kPa. What is the recommended absolute pressure?
[1 atmospheric pressure = 101 kPa] Show Answer

Q95) A small cylinder of 2 cm diameter is connected to a large cylinder of 20 cm diameter and each cylinder is fitted with suitable pistons. An incompressible fluid is filled in the cylinders. If a force of 60 N is applied to the piston of the small cylinder, then the force exerted on the piston of the large cylinder will be Show Answer

Q96) A U-tube contains water and spirit separated by mercury. The mercury columns in the two arms are in level with 10.0 cm of water in one arm and 12.5 cm of spirit in the other. What is the specific gravity of spirit? Show Answer

Q97) Two syringes of different cross-sections (without needles) filled with water are connected with a tightly fitted rubber tube filled with water. The syringes are fitted with movable pistons. Diameters of the smaller piston and larger piston are 1.0 cm and 3.0 cm respectively. What is the force exerted on the larger piston when a force of 10 N is applied to the smaller piston? Show Answer

Q98) A cylindrical vessel of radius r is filled with a homogeneous liquid upto a height h. It is found that the force exerted by the liquid column on the bottom of the cylinder is equal to the force exerted by the liquid on the sides of the cylinder. What is the relation between r and h? Show Answer

Q99) When an air bubble rises from the bottom of a lake to the surface, its radius is doubled. The atmospheric pressure is equal to that of a column of water of height H. What is the depth of the lake? Show Answer

Q100) Atmospheric pressure can be measured in terms of pascal, millibar and torr. Which is the correct relation between one torr and one millibar? Show Answer

Q101) The manual of a car recommends the owner to inflate the tyres to a pressure of 220 kPa. After the required inflation of the tyres, the owner takes the car to a mountain peak, where the atmospheric pressure is 10% less than that at the sea level. What will be the reading of the tyre guage?
[Assume that (i) At sea level, the atmospheric pressure is 100 kPa. (ii) The absolute pressure of air in the tyres not changed at the mountain peak.] Show Answer

Q102) The relative velocity of two parallel layers of water is 8 cm/s. If the perpendicular distance between the layers is 0.1 cm, then the velocity gradient will be Show Answer

Q103) Water is flowing steadily in a river. P and Q are two layers of water at heights of 20 cm and 50 cm from the bottom. The velocity of the layer A is 15 cm/sec. What is the velocity of the layer B? Show Answer

Q104) A square plate of 0.1 metre side, moves parallel to a second plate with a velocity of 0.1 m/s both plates being immersed in water. The viscous force is 0.002 newton and the coefficient of viscosity is 0.01 Poise. What is the distance between the plates? Show Answer

Q105) A metal plate of area 100 sq. cm, rests on a layer of oil 2 mm thick. A force of 0.1 N applied parallel to the plate horizontally keeps it moving with uniform speed of 1 cm/ s. What is the coefficient of viscosity of oil? Show Answer

Q106) If the Reynold's number for the flow of a liquid in a tube is 3800, then the flow of the liquid is Show Answer

Q107) The onset of turbulence in a liquid is determined by Show Answer

Q108) If a small raindrop falls through air, its velocity Show Answer

Q109) Two water drops of the same radius are falling through air with a velocity of 5 cm/s. If the two drops coalesce to form one drop, the terminal velocity of the drop will be Show Answer

Q110) 27 identical drops of water are falling down vertically in air each with a terminal velocity of 0.15 m/s. If they combine to form a single bigger drop, what will be its terminal velocity? Show Answer

Q111) Two raindrops reach the earth with different terminal velocities having the ratio 9:4. What is the ratio of their volumes? Show Answer

Q112) Two hail stones in the form of spheres with radii in the ratio 1:2, fall from a great height through the atmosphere. What is the ratio of their momenta when they attain their respective terminal velocities? Show Answer

Q113) Bernoulli's equation for a steady streamline flow of a non-viscous incompressible fluid expresses the principle of Show Answer

Q114) In old age arteries carrying blood in the human body become narrow resulting in an increase in blood pressure. This follows from Show Answer

Q115) A liquid flows through a horizontal tube of variable cross section. The pressure is lowest where the Show Answer

Q116) High speed wind blows over a house. The force on the roof is Show Answer

Q117) Water flows out of the hole on the side of a bucket and follows a parabolic path. If the bucket falls freely under gravity, then ignoring air resistance, the water flow Show Answer

Q118) There are two holes P and Q at depths h and 4h from the top of a large vessel, completely filled with water. P is a square hole of side Land Q is a circular hole of radius r. If the same quantity of water flows out per second from both the holes, then the relation between L and r is Show Answer

Q119) In a container, filled with water upto a height h, a hole is made in the bottom. The velocity of water flowing out of the hole is Show Answer

Q120) In a streamline flow if the gravitational head is h, then the kinetic and pressure heads are Show Answer

Q121) Water flows through a horizontal pipe whose internal diameter is 2.0 cm, at a speed of 1.0 m/s. What should be the diameter of the nozzle, if the water is to emerge at a speed of 4.0 m/s? Show Answer

Q122) Water is flowing in a horizontal pipe of non-uniform cross section. The velocities of water at points A and B in the tube, are in the ratio of 4: 1, what is the ratio of the diameters of the pipe at A and B? Show Answer

Q123) A tank of height 9.8 m is completely filled with water. It has an orifice at the centre of one vertical wall. What is the velocity of discharge (efflux) of water through the orifice? Show Answer

Q124) There is a stream line flow of water in a horizontal pipeline of non-uniform cross-section. The velocities of water at two points. A and B in the pipe are 1 m/s and 2 m/s. The pressure at A is 2000 pascal. What is the pressure at B? Show Answer

Q125) A tank is filled with water to a height H. A hole is made in one of the walls at a depth D below the water surface. The distance x from the foot of the wall at which the stream of water coming out of the tank strikes the ground is given by Show Answer

Q126) A gardening pipe having an internal radius R is connected to a water sprinkler having n holes each of radius r. The water in the pipe has a speed v. What is the speed of water leaving the sprinkler? Show Answer

Q127) A fluid of density p flows through a horizontal pipe having two different cross-sections of areas A and 2A. The pressure at the smaller cross-section is P and fluid velocity at that section is v. What is the velocity and pressure at the larger cross-section? Show Answer

Q128) Which one of the following graphs between velocities versus time for a body falling in viscous fluid is correct? Show Answer

Q129) If a detergent is dissolved in water, the surface tension of water Show Answer

Q130) The surface tension of a liquid is 75 dynes/cm in C.GS. system. In Sl system this is expressed as Show Answer

Q131) 125 rain drops are combined to form a single drop. The ratio of the total energy of 125 drops to that of a single drop is Show Answer

Q132) 1000 tiny mercury droplets coalesce to form a bigger drop. In this process, the temperature of the drop Show Answer

Q133) The energy needed for breaking a drop of radius R into n drops each of radius r is Show Answer

Q134) A spherical liquid drop of radius R is split up into 8 equal droplets. If T is the surface tension of the liquid, then the work done in this process is Show Answer

Q135) What is the change in surface energy, when a mercury drop of radius R splits up into 1000 droplets of radius r? [The surface tension of mercury is T.] Show Answer

Q136) If the surface area of any liquid surface is increased by 50%, then its surface tension will Show Answer

Q137) Small droplets of a liquid are usually more spherical in shape than the larger drops of the same liquid because Show Answer

Q138) What is ratio of surface energies of 1 small drop and 1 large drop, if 1000 small drops are combined to from 1 large drop? Show Answer

Q139) Molecules on the surface of a liquid in equilibrium possess Show Answer

Q140) What is the unit of surface tension? Show Answer

Q141) The P.E. of a molecule of a liquid on the surface of the liquid when compared to its P.E., when inside the liquid is Show Answer

Q142) A mercury drop of radius R splits up into 1000 droplets of equal radii. The change in the surface area is Show Answer

Q143) Two small drops of mercury each of radius R coalesce to form a single drop. The ratio of the total surface energies before and after the change is Show Answer

Q144) A water drop of radius R is split into n smaller drops, each of radius r. If T is the surface tension of water, then the work done in this process is Show Answer

Q145) A metallic wire of length L and density d floats horizontally on the surface of water. What should be the maximum radius of the wire, so that the wire will not sink in water? Show Answer

Q146) Which is the fundamental unit that has the same power in the dimensional formulae of surface tension and coefficient of viscosity? Show Answer

Q147) A wooden stick 2 m long is floating on the surface of water. The surface tension of water is 0.07 N/m. By putting soap on one side of the stick, the surface tension of water is reduced to 0.06 N/m. What is the net force on the stick? Show Answer

Q148) A certain number of spherical drops of a liquid of radius 'r' coalesce to form a single drop of radius 'R' and volume 'V'. If 'T' is the surface tension of the liquid, then: Show Answer

Q149) A liquid rises to a height of 10 cm in a capillary tube of height 16 cm and radius 1 mm, above the liquid level. If the tube is cut at a height of 8 cm, then Show Answer

Q150) Choose the wrong statement from the following. Show Answer

Q151) Water rises upto a height h in a capillary tube on the surface of the earth. The value of h increases, if the capillary tube apparatus is kept Show Answer

Q152) A glass plate is partly dipped vertically in mercury and the angle of contact is measured. If the plate is made inclined to the vertical then the angle of contact will Show Answer

Q153) In which one of the following phenomena capillary action is not used? Show Answer

Q154) A liquid rises to a height of 1.8 cm in a glass capillary ‘A’ another glass capillary ‘B’ having diameter 90% of capillary ‘A’ is immersed in the same liquid the rise of liquid in capillary ‘B’ is Show Answer

Q155) The surface tension for pure water in a capillary tube experiment is Show Answer

Q156) A capillary tube having 1 mm and 2.5 mm as internal and external radii hangs vertically from the arm of a balance. The lower end of the tube just touches a liquid of surface tension 40 dyne/cm. If the angle of contact is zero, then the change in weight due to surface tension is Show Answer

Q157) If a capillary tube of radius 1 mm is immersed in water, the mass of water rising in the capillary tube is M. If the radius of the capillary tube is doubled, then the mass of water that rises in the capillary tube will be Show Answer

Q158) Pure water rises through a height h in a capillary tube of internal radius (r). If T is the S.T. of water, then the pressure difference between the water level in the container and the lowest point of the concave meniscus is Show Answer

Q159) For which of the two pairs, the angle of contact is of the same nature? Show Answer

Q160) The height upto which water will rise in a capillary tube will be Show Answer

Q161) The lower end of a glass capillary tube is dipped in water. Water rises to a height of 8 cm. The tube is then broken at a height of 6 cm. Then the height of the water column and the angle of contact will be Show Answer

Q162) A capillary tube of radius 'r' is immersed in water and water rises in it upto a height h. The mass of water lifted in the capillary tube is 5 g. Another capillary tube of radius 2r is immersed in water. What is the mass of water that will rise in the second tube? Show Answer

Q163) The lower end of a capillary tube of radius r cm is placed vertically in water. What is the heat evolved if water rises upto a height h in the capillary tube? Show Answer

Q164) Water rises to a height of 2 cm in a capillary tube. The angle of contact is zero. The tube is now depressed further so that its length above the surface of water is only 1 cm. What is the new apparent angle of contact? Show Answer

Q165) A square frame of side L is dipped in a soap solution. When it is taken out of the solution, a film is formed on it. If the surface tension is T, then force acting on it is: Show Answer

Q166) The work done in blowing a soap bubble of 10 cm radius is (surface tension of soap solution = 3/100 N/m) Show Answer

Q167) The surface tension of soap solution is 30 dyne/cm. A soap bubble made from this solution has a radius of 1 cm. The work done in doubling the radius of the soap bubble is Show Answer

Q168) If T is the surface tension of a soap solution, then the work done in blowing a soap bubble from diameter D to diameter 2D is given by Show Answer

Q169) A sheet can be made water proof by coating it with a substance that changes the angle of contact Show Answer

Q170) W is the work done, when a bubble of volume V is formed from a solution. How much work is required to be done to form a bubble of volume 2V? Show Answer

Q171) Air is pushed in a soap bubble to increase its radius from R to 2R. In this case the pressure inside the bubble Show Answer

Q172) At critical temperature, the surface tension of a liquid Show Answer

Q173) If the excess pressure inside a soap bubble of radius 5 mm is equal to the pressure of a water column of height 0.8 cm, then the surface tension of the soap solution will be Show Answer

Q174) When a soap bubble is charged Show Answer

Q175) If the radius of a soap bubble is four times that of another, then the ratio of their excess pressures will be Show Answer

Q176) The surface tension of pure water is measured at different temperatures. It is found that the surface tension is minimum when the temperature of water is Show Answer

Q177) When one end of a capillary tube is dipped vertically in water, the pressure below the meniscus of water is Show Answer

Q178) 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 a deep water bath (surface tension T) without any water entering inside is Show Answer

Q179) The surface tension of soap solution is 0.030 N/m. What is the energy needed to increase the radius of a soap bubble from 4 cm to 6 cm? Show Answer

Q180) Work done in increasing the size of a soap bubble from a radius of 3 cm to 5 cm is nearly (Surface tension of soap solution = 0.03 N/m) Show Answer

Q181) When NaCl is added to water, the surface tension of water will Show Answer

Q182) With an increase in temperature, surface tension of a liquid (except molten cadmium and copper) Show Answer

Q183) If two soap bubbles of equal radii (r and r) coalesce, then the radius of curvature of the interface between the two bubbles will be Show Answer

Q184) The pressure inside a soap bubble A is 1.01 atmosphere and that in a soap bubble B is 1.02 atmosphere. What is the ratio of the volumes of A and B? Show Answer

Q185) A soap bubble assumes a spherical surface. Which one of the following statement is wrong? Show Answer

Q186) A soap bubble is blown by using 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. Which one of the following graphs correctly represents the relation between excess pressure (AP) inside the air bubble and the time? Show Answer

Q187) In which of the following substances, the surface tension increases with an increase in temperature? Show Answer

Q188) A big water drop of radius R is formed from 1000 droplets of water. The radius of the droplet will be Show Answer

Q189) n droplets of equal size and each of radius r coalesce to form a bigger drop of radius R. The energy liberated is equal to
(T- Surface tension of water) Show Answer

Q190) In a capillary tube of radius 'R', a straight thin metal wire of radius 'r' (R > r) is inserted symmetrically and one end of the combination is dipped vertically in water such that the lower end of the combination is at the same level. The rise of water in the capillary tube is
[T = surface tension of water, rho = density of water, g = gravitational acceleration] Show Answer

Q191) A liquid drop having surface energy ‘E’ is spread into 512 droplets of the same size. The final surface energy of the droplets is Show Answer