Ans : (d)
48. The following processes take place during the launching of a rocket: [CDS1995]
       1) Rocket fuel is burnt.
       2) Gases are produced.
       3) Rocket moves in the forward direction
       4) Gases come out with momentum in backward direction.
       The correct sequential order, in which the above processes occur, is:
       (a)  1,2, 3,4
       (b)  1,3, 2,4
       (c)  1,2, 4, 3
       (d)  1,3,4, 2
Ans : (c)
49. To achieve high value of rocket velocity one must have:
       (a) high exhaust velocity and low loss of mass during propulsion
       (b) high exhaust velocity and higher loss of Mass during propulsion
       (c) low exhaust velocity and higher loss of Mass during propulsion
       (d) None of the above
Ans : (b)
50. Aviation fuel for jet aeroplanes consists of purified:
       (a) petrol
       (b) kerosene
       (c) gasoline
       (d) diesel
Ans : (b)
51. Recoil of a gun is an example of:
       (a) conservation of mass
       (b) conservation of energy
       (c) conversion of. P.E. into K.E.
       (d) conservation of linear momentum
Ans : (d)
52. Which of the following polymers is widely used for making bullet proof material? [IAS1995]
       (a) Polyethylene
       (b) Polyamides
       (c) Polyvinyl chloride
       (d) Polycarbonates
Ans : (a)
53. The following are some great discoveries in Physics: [NDA1990]
       1) X-rays
       2) Theory of relativity
       3) Super conductivity
       4) Raman effect
       The chronological order in which they were discovered is:
       (a) 1,2, 3,4
       (b) 1,2, 4, 3
       (c) 1, 3, 2, 4