Select the correct answer using the code given below: [NDA 2010]
     (a)   1 and 3
     (b)   2 only
     (c)   2 and 3
     (d)   1, 2 and 3
Ans : (a)
306. By which one among the following mechanism, soap removes dirt (soil) from cloth? [NDA 2010]
       (a) Soap dissolves the soil as such
       (b) Soap reacts with soil and converts them into soluble silicates
       (c) Soap takes away the oily part of the soil and thus separates the soil from the cloth
       (d) The soap molecules bind with the soil, lift the soil and keep it suspended which can then be rinsed away
Ans : (c)
307. A pendulum beats faster than a standard pendulum. In order to bring it to the standard beat, the length of the pendulum is to be :
     [NDA 2010]
       (a) reduced
       (b) increased
       (c) reduced and the mass of the bob increased
       (d) reduced and also the mass of the bob reduced
Ans : (b)
308. When a ship floats on water: [NDA 2010]
       (a) it displaces no water
       (b) the mass of water displaced is equal to the mass of the ship
       (c) the mass of water displaced is lesser than the mass of the ship
       (d) the mass of water displaced is greater than the mass of the ship
Ans : (b)
309. Hydrogen fuel cell vehicles produce one of the following as "exhaust" [IAS 2010]
        (a) NH3
        (b) CH4
        (c) H2O
        (d) H2O2
Ans : (c)
310. The best colours for a Sun umbrella will be [CDS 2012]
        (a) black on top and red on inside
        (b) black on top and white on inside
        (c) red on top and black on inside
        (d) white on top and black on inside
Ans : (d)
311. Lack of atmosphere around the Moon is due to [CDS 2012]
        (a) low escape velocity of air molecule and low gravitational attraction
        (b) high escape velocity of air molecule and low gravitational attraction
        (c) low gravitational attraction only
        (d) high escape velocity of air molecule only
Ans : (c)
312. In SONAR, we use [CDS 2012]
                                                                   251