21) Large astronomical telescopes always use as objective
a) lens
b) mirror
c) combinations of lenses
d) None of the above
22) Find the maximum velocity for the overturn of a car moving on a circular track of radius 100 m. The co-efficient of friction between the road and tyre is 0.2
a) 0.14 m/s
b) 140 m/s
c) 1.4 km/s
d) 14 m/s
23) Radiocarbon is produced in the atmosphere as a result of
a)collision between fast neutrons and nitrogen nuclei present in the atmosphere
b)action of ultraviolet light from the sun on atmospheric oxygen
c)action of solar radiations particularly cosmic rays on carbon dioxide present in the atmosphere
d)lightning discharge in atmosphere
24) Which of following in not a property of cathode ray.
a)Cathode rays are invisible and travel in a straight line.
b)These rays can ionise gases.
c)These rays can penetrate through thin metal foils.
d)These rays make materials cool on which they fall.
25) Siphon will fail to work if
a)both its limbs are of unequal length
b)the temperature of the liquids in the two vessels are the same
c)the level of the liquid in the two vessels are at the same height
d)the densities of the liquid in the two vessels are equal
26) Which are the primary Colours ?
a)Yellow, Green, Blue
b)Red, Magenta, Blue
c)Red, Green, White
d)Red, Green, Blue
27) Of the four locations mentioned below the highest inside temperature will be attained in the pressure cooker operated with the pressure valve open
a) at sea level
b) at the top of Mt. Everest
c) at a place in a valley below sea level
d) in an aeroplane flying at a height of 10,000 m with inside pressure maintained at the sea level
28) Planets do not twinkle because
a) they emit light of a constant intensity
b) their distance from the earth does not change with time
c) they are very far away from the earth resulting in decrease in intensity of light
d) they are nearer to earth and hence we receive a greater amount of light and, therefore minor variations in the intensity are not noticeable
29) Railway tracks are banked on curves
a) necessary centrifugal force may be obtained from the horizontal component weight of the train
b) to avoid frictional force between the tracks and wheels
c) necessary centripetal force may be obtained from the horizontal component of the weight of the train
d) the train may not fly off in the opposite direction
30) With the increase of pressure, the boiling point of any substance
a) Increases
b) Decreases
c) Remains Same
d) Becomes zero