(d) it is made of a denser material
Ans : (c)
66. What happens to the level of mercury in the barometer tube when it is taken down a coal mine? It
       (a) falls
       (b) remains unaltered
       (c) rises
       (d) rises and then falls
Ans : (c)
67. For a simple pendulum in Simple harmonic motion, which of the following statements is/are correct? [NDA 2010]
       1) The kinetic energy is maximum at the mean position.
       2) The potential energy is maximum at the mean position. .
       3) Acceleration is maximum at the mean position.
       (a) 1 only
       (b) 2 only
       (c) 1 and 3
       (d) 2 and 3
Ans : (c)
68. In our houses we get 220 V A.C. What does the value 220 represent?
       (a) Constant voltage
       (b) Effective voltage
       (c) Average voltage
       (d) Peak voltage
Ans : (b)
69. The quality of a sound depends upon the:
       I.    size of the vibrating body
     II.     material of the vibrating body
    III.     overtones produced
    IV.      shape of the vibrating body
     (a) I, II and III
     (b) I, II, III and IV
     (c) I and III
     (d) II, III and IV
Ans : (b)
70. Which of the following statements is/are true?
         I.    Sound is a form of energy.
        II.    Sound stops when vibration of an object stops.
      III.     Sound is a transverse wave.
      IV.      Sound travels better in a heavy gas than in a light gas.
     (a) I and II
     (b) I, II and III
     (c) I, II and IV
     (d) I and III
Ans : (c)
71. In a barometer, mercury is preferred over water because:
     (a) mercury is a good conductor of heat
     (b) mercury shines and therefore its level can be read easily
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