Question 51. A liquid rises in a capillary tube when the angle of contact is________
Answer: an acute angle
Question 52. The hydraulic brakes used in automobiles is a direct application of________
Answer: Pascal’s Law
Question 53. A periscope works by the principle of________
Answer: Reflection and refraction
Question 54. Super conductors are those materials which________
Answer: looses all electrical resistance when cooled below a certain temperature
Question 55. Bat can fly in the dark because they are guided by______ waves produced by them.
Question 56. A solid piece of iron sinks in water but floats in mercury. This is because the________
Answer: Density of iron is more than that of water but less than that of mercury
Question 57. A red object, when seen through a thick blue glass, appears________
Question 58. ________ is the cause of weightlessness experienced while orbiting around earth on a spaceship.
Answer: Zero gravity
Question 59. If two bodies are completely covered with water, they have________
Answer: same density
Question 60. In a reactor, Cadmium rods are used for________
Answer: Absorbing neutrons
Question 61. Radar is based on the principle that________
Answer: Radio waves are reflected by objects
Question 62. For a given velocity of projection, the maximum range of a projectile can be achieved if the angle of projection is________
Question 63. Detergents dissolved in water help in cleaning clothes by________
Answer: reducing the surface tension of water
Question 64. An aeroplane rises because________
Answer: the pressure above its wings is less than the pressure below them.
Question 65. An ordinary clock loses time during summer because the length of the pendulum________
Answer: increases and therefore the time period increases
Question 66. The apparent weight of a man in a lift is less than his real weight________
Answer: when the lift is going down with uniform acceleration
Question 67. Light from the Sun reaches us in nearly________
Answer: 8 minutes
Question 68. A boat loaded with rocks floats in the middle of a swimming pool and a man in the boat throws rocks over board in water. The water level of the pool will___
Answer: be lowered
Question 69. A tennis ball will bounce higher on_____than on plains.
Answer: higher on hills than on plains
Question 70. The leaning tower of Pisa does not fall because______
Answer: the vertical li ne through the C.G. of the tower falls within its base.
Question 71. A man carrying a load on his back bends forward because of one of________
Answer: To adjust the C.G. of the system such that the vertical line through the C.G. passes within the base.
Question 72. When milk is churned cream gets separated due to__
Answer: centrifugal force
Question 73. Production of beats is a result of the phenomenon of__
Question 74. The internal resistance of ____ of the instruments is the highest.
Question 75. Siphon will fail to work if the level of the liquid in the two vessels are at the________height.
Question 76. The nature of light waves is similar to________rays.
Question 77. If the radius of the earth were to shrink by one per cent, its mass remaining the same, the acceleration due to gravity on earth’s surface would________
Question 78. A dental plate clings to the roof of the mouth because________
Answer: force of adhesion increases
Question 79. At absolute zero of temperature the molecular energy is________
Answer: minimum but not zero
Question 80. The half life of a substance is 10 days. How much of the substance will be left after 40 days if initial mass is 2 gm________
Answer: 0.125 gm.
Question 81. Angstrom is equal to________nanometer.
Question 82. A cricketer lowers his hand while catching the ball. This saves him from injury because of________
Answer: conservation of momentum
Question 83. One litre of cool air weighs heavier than one litre of dry air because of the________
Answer: increased number of molecules at high temperature
Question 84. A piece of rock was brought from moon to earth. Then its weight________
Answer: alone changed
Question 85. Diamond is harder than graphite because of difference of________
Answer: crystalline structures
Question 86. Four identical kettles with the same amount of water have bases made of brass, copper, steel and aluminium metals of the same thickness. If these kettles are placed on identical flames in an identical manner, water will boil first in the kettle the base of which is made of________
Question 87. The principle underlying a microwave oven is________
Answer: microwaves vibrat e the water molecules in food thereby generating heat.
Question 88. ________is a good conductor of heat and electricity.
Question 89. Why ________is platinum wire used inside very narrow glass rods?
Answer: Platinum and glass have the same linear coefficients of expansion
Question 90. Grass looks green because________
Answer: it absorbs all the colours in the spectrum except green
Question 91. Persistence of vision is the principle behind________
Question 92. Television signals cannot be received ordinarily beyond a particular distance due to________
Answer: curvature of the earth
Question 93. Cones in the retina of eyes (about 6 million) are concerned with________
Answer: colour disc rimination and acute discrimination of detail
Question 94. A fisherman sitting on the bank of a pond trying to spear a fish should aim________
Answer: a little below where he sees the fish
Question 95. The comic mirrors seen in amusement parks have reflecting surfaces that are________
Answer: irregularly curved
Question 96. The total internal reflection occurs when the angle of incidence is________than the critical angle.
Question 97. After rains if the sun is shining brightly in one part of the sky, ________rainbows are observed.
Question 98. In cold countries glycerol is added to water in car radiators as it helps to________
Answer: lower the freezing point of water
Question 99. You can hear the roar of the sea on holding a sea shell to your ear because________
Answer: the effect of multi-reflections of air producing a vibrating sound
Question 100. A tape-recorder’s tape is coated with a________
Answer: ferromagnetic substance powder