Ans : (d)
15. Water kept in an old surahi is less cold than the water in a new one. Why?
     (a) The pores in the surahi help in evaporation of water
     (b) The pores in the old surahi become clogged and thus, the total surface area for evaporation is reduced
     (c) Old surahi become saturated with water and hence evaporation is not rapid
     (d) None of the above
Ans : (b)
16. The best conductor of electricity is :
     (a) filtered hot water
     (b) distilled water
     (c) filtered water at room temperature
     (d) salt water
Ans : (d)
17. Which of the following is the correct sequence of the regions of the sun as one moves from its core to the surface?
     1) Photosphere
     2) Chromosphere
     3) Convection zone
     4) Corona
     (a) 1,2,3,4
     (b) 1,3,4,2
     (c) 2, 3,4 1
     (d) 2, 1, 3, 4
Ans : (a)
18. You are standing in a lift. The force on the floor of the lift due to your weight will :
     (a) become zero when the lift moves up with an acceleration of 9.8 m/s 2
     (b) become zero when the lift moves down with an acceleration of 9.8 m/s 2
     (c) become zero when the lift moves with an acceleration of 9.8 m/s 2 in any direction
     (d) remain unchanged whatever be the value of acceleration of the lift
Ans : (b)
19. If the earth were 3 times as far from the sun as it is now, how would the gravitational attraction compare with its present value?
     (a) The gravitational attraction would be 9 times its present amount
     (b) The gravitational attraction would be double its present amount
     (c) The gravitational attraction would be 1/9 of its present amount
     (d) None of the above would be true
Ans : (c)
20. Two cars, passing each other at high speed, are in danger of side swiping because:
     (a) of the increase in air pressure in the space between them
     (b) of decrease in the velocity of air molecules between them
     (c) of decrease in air pressure in the space between them
     (d) increase in the velocity of air molecules between them
Ans : (c)
21. What is the correct ascending order for frequencies of the following radiations? [CDS 1990]
     1) Visible
     2) X-rays
     3) Ultraviolet
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