217. When a lift is going down with uniform acceleration, the apparent weight of a man in the lift is :
       (a) more than the real weight
       (b) slightly less than the real weight
       (c) equal to the real weight
       (d) zero
Ans : (b)
218. Which one of the following properties of glass isused in green house to trap heat on a sunny day?
       (a) It is transparent to short wave radiation but obstruct the long wave infrared radiation
       (b) It is transparent to long infrared radiation emitted by very hot objects
       (c) It obstructs the short wave infrared radiation, emitted by very hot objects
       (d) None of the above
Ans : (a)
219. Soldiers crossing a suspension bridge, always break steps, in case the frequency of vibration of their marching, should coincide with
     that of the bridge and this is because of the phenomenon of:
       (a) refraction of sound
       (b) reverberation of sound
       (c) resonance of sound
       (d) echolocation of sound
Ans : (c)
220. In a cup, tea cools from 90°C to 80°C in exactly one minute. It will cool from 70°C to 60°C in:
       (a) less than one minute
       (b) exactly one minute
       (c) nearly one minute
       (d) more than one minute
Ans : (a)
221. A person is moving towards a plane mirror with a speed of 1 m/sec. The image will approach the moving person with a relative
     speed of:
       (a) 1/2 m/sec
       (b) 1m/sec
       (c) 2 m/sec
       (d) 3 m/sec
Ans : (c)
222. Two men talk on moon:
       (a) they hear each other with lower frequency
       (b) they hear each other with higher frequency
       (c) they can hear each other with the same frequency as on earth
       (d) they can"t hear each other at all
Ans : (d)
223. We cannot see during a fog because of:
       (a) reflection of light
       (b) internal reflection
       (c) refraction
       (d) scattering of light
Ans : (d)