Tiêu đề 10. Surface Tension Easy.pdf ✅

1. The value of surface tension of a liquid at critical temperature is (a) Zero (b) Infinite (c) Between 0 and  (d) Can not be determined 2. The spherical shape of rain-drop is due to (a) Density of the liquid (b) Surface tension (c) Atmospheric pressure (d) Gravity 3. Surface tension is due to (a) Frictional forces between molecules (b) Cohesive forces between molecules (c) Adhesive forces between molecules (d) Gravitational forces 4. When there is no external force, the shape of a liquid drop is determined (a) Surface tension of the liquid (b)Density of liquid (c) Viscosity of liquid (d)Temperature of air only 5. Soap helps in cleaning clothes, because (a) Chemicals of soap change (b) It increases the surface tension of the solution (c) It absorbs the dirt (d) It lowers the surface tension of the solution 6. A pin or a needle floats on the surface of water, the reason for this is (a) Surface tension (b) Less weight (c) Upthrust of liquid (d) None of the above 7. Coatings used on raincoat are waterproof because (a) Water is absorbed by the coating (b) Cohesive force becomes greater (c) Water is not scattered away by the coating (d) Angle of contact decreases 8. If temperature increases, the surface tension of a liquid (a) Increases (b) Decreases (c) Remains the same (d) Increases then decreases 9. A drop of oil is placed on the surface of water. Which of the following statement is correct (a) It will remain on it as a sphere (b) It will spread as a thin layer (c) It will be partly as spherical droplets and partly as thin film (d) It will float as a distorted drop on the water surface 10. The temperature at which the surface tension of water is zero (a) 0°C (b) 277 K (c) 370°C (d) Slightly less than 647 K 11. 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 (a) Increase in the saturated vapour pressure of water (b) Root mean square velocity of air molecules inside the bubble increases (c) Decrease in surface tension of water (d) All of the above 12. The spiders and insects move and run about on the surface of water without sinking because (a) Elastic membrane is formed on water due to property of surface tension (b) Spiders and insects are lighter (c) Spiders and insects swim on water (d) Spider and insects experience up thrust 13. Small droplets of a liquid are usually more spherical in shape than larger drops of the same liquid because (a) Force of surface tension is equal and opposite to the force of gravity (b) Force of surface tension predominates the force of gravity (c) Force of gravity predominates the force of surface tension (d) Force of gravity and force of surface tension act in the same direction and are equal 14. Hairs of shaving brush cling together when it is removed from water due to (a) Force of attraction between hair (b) Surface tension (c) Viscosity of water (d) Characteristic property of hairs 15. 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 (a) 2 TL (b) 4 TL (c) 8 TL (d) 10 TL 16. Water does not wet an oily glass because (a) Cohesive force of oil>> adhesive force between oil and glass (b) Cohesive force of oil > cohesive force of water (c) Oil repels water (d) Cohesive force for water > adhesive force between water and oil molecules 17. A water drop takes the shape of a sphere in a oil while the oil drop spreads in water, because (a) C.F. for water > A.F. for water and oil (b) C.F. for oil > A.F. for water and oil (c) C.F. for oil < A.F. for water and oil (d) None of the above

(a) Surface tension is more (b) Surface tension is less (c) Consumes less soap (d)None of these 37. Due to which property of water, tiny particles of camphor dance on the surface of water (a) Viscosity (b) Surface tension (c) Weight (d) Floating force 38. The force required to separate two glass plates of area 2 2 10 m − with a film of water 0.05 mm thick between them, is (Surface tension of water is 3 70 10 −  N/m) (a) 28 N (b) 14 N (c) 50 N (d) 38 N 39. Oil spreads over the surface of water whereas water does not spread over the surface of the oil, due to (a) Surface tension of water is very high (b) Surface tension of water is very low (c) Viscosity of oil is high (d) Viscosity of water is high 40. Cohesive force is experienced between (a) Magnetic substances (b) Molecules of different substances (c) Molecules of same substances (d) None of these 41. The property utilized in the manufacture of lead shots is (a) Specific weight of liquid lead (b) Specific gravity of liquid lead (c) Compressibility of liquid lead (d) Surface tension of liquid lead 42. The dimensions of surface tension are (a) [MLT −1 ] (b) [ML 2T −2 ] (c) [ML 0T −2 ] (d) [ML −1T −2 ] 43. 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 (a) 0.07 N (b) 0.06 N (c) 0.01 N (d) 0.02 N 44. A thread is tied slightly loose to a wire frame as in figure and the frame is dipped into a soap solution and taken out. The frame is completely covered with the film. When the portion A punctured with a pin, the thread. (a) Becomes concave toward A (b) Becomes convex towards A (c) Remains in the initial position (d) Either (a) or (b) depending on the size of A w.r.t. B 45. 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) (a) 280 dyne (b) 250 dyne (c) 140 dyne (d) 210 dyne 46. Surface tension may be defined as (a) The work done per unit area in increasing the surface area of a liquid under isothermal condition (b) The work done per unit area in increasing the surface area of a liquid under adiabatic condition (c) The work done per unit area in increasing the surface area of a liquid under both isothermal and adiabatic conditions (d) Free surface energy per unit volume 47. Energy needed in breaking a drop of radius R into n drops of radii r is given by (a) 4πT(nr 2 − R 2 ) (b) 4 3 π(r 3n − R 2 ) (c) 4πT(R 2 − nr 2 ) (d) 4πT(nr 2 + R 2 ) 48. The potential energy of a molecule on the surface of liquid compared to one inside the liquid is (a) Zero (b) Smaller (c) The same (d) Greater 49. Two droplets merge with each other and forms a large droplet. In this process (a) Energy is liberated (b) Energy is absorbed (c) Neither liberated nor absorbed (d) Some mass is converted into energy 50. 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) (a) Zero (b) 19 erg (c) 46 erg (d) 74 erg 51. 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 (a) 4πr 2T (b) 2πr 2T (c) 12πr 2T (d) 24πr 2T 52. Work done in splitting a drop of water of 1 mm radius into 106 droplets is (Surface tension of water = 72 × 10 −3 J/m2 ) (a) 9.58 × 10 −5 J (b) 8.95 × 10 −5 J A B Thread Frame
(c) 5.89 × 10 −5 J (d) 5.98 × 10 −6 J 53. 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 (a) 2πR 2T (b) 3πR 2T (c) 4πR 2T (d) 2πRT 2 54. 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) (a) 4π(D 2 − d 2 )T (b) 8π(D 2 − d 2 )T (c) π(D 2 − d 2 )T (d) 2π(D 2 − d 2 )T 55. 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 (a) 2 D T 2  (b) 4 D T 2  (c) 6 D T 2  (d) 8 D T 2  56. The radius of a soap bubble is increased from  1 cm to  2 cm. If the surface tension of water is 30 dynes per cm, then the work done will be (a) 180 ergs (b) 360 ergs (c) 720 ergs (d) 960 ergs 57. The surface tension of a liquid is 5 N/m. If a thin film of the area 0.02 m2 is formed on a loop, then its surface energy will be (a) 5 × 10 2 J (b) 2.5 × 10 −2 J (c) 2 × 10 −1 J (d) 5 × 10 −1 J 58. 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 (a) W/2 (b) 2W (c) 4W (d) 3 1 2 W 59. 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 (a) 18  ergs (b) 180  ergs (c) 1800  ergs (d) 8000  ergs 60. The work done in blowing a soap bubble of radius r of the solution of surface tension T will be (a) 8πr 2T (b) 2πr 2T (c) 4πr 2T (d) 4 3 πr 2T 61. If two identical mercury drops are combined to form a single drop, then its temperature will (a) Decrease (b) Increase (c) Remains the same (d) None of the above 62. If the surface tension of a liquid is T, the gain in surface energy for an increase in liquid surface by A is (a) AT −1 (b) AT (c) A 2T (d) A 2T 2 63. The surface tension of a soap solution is2 × 10 −2N/m. To blow a bubble of radius 1 cm, the work done is (a) 4π × 10 −6 J (b) 8π × 10 −6 J (c) 12π × 10 −6 J (d) 16π × 10 −6 J 64. A mercury drop of 1 cm radius is broken into 10 6 small drops. The energy used will be (surface tension of mercury is 35 × 10 −3N/cm) (a) 4.4 × 10 −3 J (b) 2.2 × 10 −4 J (c) 8.8 × 10 −4 J (d) 10 4 J 65. The surface tension of a liquid at its boiling point (a) Becomes zero (b) Becomes infinity (c) is equal to the value at room temperature (d) is half to the value at the room temperature 66. Surface tension of a soap solution is 1.9 × 10 −2N/m.. Work done in blowing a bubble of 2.0 cm diameter will be (a) 7.6 × 10 −6πjoule (b) 15.2 × 10 −6πjoule (c) 1.9 × 10 −6πjoule (d) 1 × 10 −4 joule 67. The surface tension of liquid is 0.5 N/m. If a film is held on a ring of area 0.02 m2 , its surface energy is (a) 5 × 10-2 joule (b) 2.0 × 10-2 joule (c) 4 × 10-4 joule (d) 0.8 × 10-1 joule 68. What is ratio of surface energy of 1 small drop and 1 large drop, if 1000 small drops combined to form 1 large drop (a) 100 : 1 (b) 1000 : 1 (c) 10 : 1 (d) 1 : 100 69. The amount of work done in forming a soap film of size 10cm × 10cmis (Surface tension T = 3 × 10 −2N/m) (a) 6 × 10 −4 J (b) 3 × 10 −4 J (c) 6 × 10 −3 J (d) 3 × 10 −4 J 70. The work done in blowing a soap bubble of 10 cm radius is (Surface tension of the soap solution is 3 100 N/m) (a) 75.36 × 10 −4 joule (b) 37.68 × 10 −4 joule (c) 150.72 × 10 −4 joule (d) 75.36joule