Ans : (d)
237. Which law is involved in the act of cleaning a carpet by beating it with a stick?
       (a) First law of motion
       (b) Second law of motion
       (c) Law of conservation of energy
       (d) Law of conservation of mass
Ans : (a)
238. A tight-rope walker carries a long pole which he holds across his body. The purpose of this pole is to :
       (a) prop him if he falls
       (b) spread out his weight and reduce the pressure on the wire
       (c) add extra weight to keep the wire tightly stretched
       (d) alter the position of the centre of gravity
Ans : (d)
239. Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this?
           1) Diffusion
           2) Refraction
           3) Internal reflection
       (a) 1, 2 and 3
       (b) 1 and 2
       (c) 2 and 3
       (d) 1 and 3
Ans : (c)
240. Lightning is formed when: [lAS 2003]
       (a) similar charges of electricity rush towards each other and then get repelled
       (b) clouds strike against impurities in air and the friction burns up these impurities
       (c) strong opposite charges in different clouds break down the resistance offered by the intervening air
       (d) water vapour produces electricity in the clouds
Ans : (c)
241. Though the temperature inside lighted electric bulb is around 2700°C, the filament does not burn because:
       (a) the metal of which it is made is resistant to burning
       (b) the oxygen necessary for combustion (and burning) is not available as the bulb is evacuated and filled with pure nitrogen or
           inert gases
       (c) it does not burn in closed systems
       (d) it is made of non-metallic substance
Ans : (b)
242. Consider the following statements: [lAS2002]
          1) Light of longer wavelength is scattered much more than the light of shorter wavelength.
          2) The speed of visible light in water is 0.95 times the speed in vacuum.
          3) Radio waves are produced by rapidly oscillating electrical currents.
          4) To detect the over speeding vehicles, police use the Doppler effect of reflected short radio waves. Which of these
                statements are correct?
       (a) 1 and 2
       (b) 1 and 3
       (c) 2 and 4
       (d) 3 and 4
Ans : (d)