some important S&T question

1. Over 90% of the world’s biomass is in–
(A) tropical rain forests (B) freshwater wetlands
(C) topsoils (D) oceans (Ans : D)

2. Which one of the following is a source of methane emission into the atmosphere ?
(A) Automobile exhaust fume (B) Industrial chimney
(C) Mining (D) Wetland (Ans : D)

3. Which one of the following statements is not correct?
(A) Trophic dynamics represents the transfer of energy from one trophic level to another in a food chain
(B) In deeper parts of oceans, primary production remains almost nil
(C) The primary consumers are called autotrophs
(D) The decomposers are called saprotrophs (Ans : C)

4. Carbon dioxide is called a greenhouse gas because–
(A) its concentration remains always higher than other gases. (B) it is used in photosynthesis.
(C) it absorbs infrared radiation. (D) it emits visible radiation. (Ans : C)

5. The fossil of Archaeopteryx represents the evidence of origin of–
(A) birds from reptiles (B) mammals from reptiles
(C) reptiles from amphibians (D) mammals from birds (Ans : A)

16. Lack of atmosphere around the Moon is due to–
(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)

17. Which one of the following correctly defines a unit magnetic pole in SI units?
It is the pole which when placed in air at a distance of–
(A) 1 foot from an equal and a similar pole repels it with a force of 1 pound.
(B) 1 metre from an equal and a similar pole repels it with a force of 1 newton.
(C) 1 cm from an equal and a similar pole repels it with a force of 1 dyne.
(D) 1 metre from an equal and a similar pole repels it with a force
of 1 newton/m2. (Ans : C)

18. After rising a short distance, the smooth column of smoke from a cigarette breaks up into an irregular and random pattern. In a similar fashion, a stream of fluid flowing past an ‘obstacle breaks up into eddies and vortices which give the flow irregular velocity components transverse to the flow direction. Other examples include the wakes left in water by moving ships, the sound produced by whistling and by wind instruments. These examples are the results of–
(A) laminar flow of air. (B) streamline flow of air.
(C) turbulent flow of air. (D) viscous flow at low speed. (Ans : D)

19. Two identical piano wires have same fundamental frequency when kept under the same tension. What will happen if tension of one of the wires is slightly increased and both the wires are made to vibrate simultaneously ?
(A) Noise (B) Beats
(C) Resonance (D) Non-linear effects (Ans : B)

20. What is the major role of a greenhouse gas that contributes to temperature rise of the Earth’s surface?
(A) Transparent to both incoming sunlight aria outgoing infrared radiation
(B) Stops both incoming sunlight and outgoing infrared radiation
(C) Lets outgoing infrared radiation pass through but stops incoming sunlight
(D) Lets incoming sunlight pass through but stops outgoing infrared radiation (Ans : D)
49. The best colours for a Sun umbrella will be–
(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)

50. Before X-ray examination (coloured X-ray) of the stomach, patients are given suitable salt of barium because–
(A) barium salts are white in colour and this helps stomach to appear clearly.
(B) barium is a good absorber of X-rays and helps stomach to appear dearly.
(C) barium salts are easily available.
(D) barium allows X-rays to pass through the stomach. (Ans : B)

51. The elements of a group in the periodic table–
(A) have similar chemical properties. (B) have consecutive atomic numbers.
(C) are isobars. (D) are isotopes. (Ans : A)

52. Which one of the following polymers is used for making bulletproof material ?
(A) Polyvinyl chloride (B) Polystyrene
(C) Polyethylene (D) Polyamide (Ans : C)

53. The pH of human blood is normally around–
(A) 4.5–5.5 (B) 5.5–6.5
(C) 7.5–8.0 (D) 8.5–9.0 (Ans : C)

54. The pH of fresh groundwater slightly decreases upon exposure to air because–
(A) carbon dioxide from air is dissolved in the water.
(B) oxygen from air is dissolved in the water.
(C) the dissolved carbon dioxide of the groundwater escapes into air.
(D) the dissolved oxygen of the groundwater escapes into air. (Ans : A)