BPSC-68 (Prelims) Science
■ Science Questions & Answers
(A) a zebra of black stripes
(B) a horse of black stripes
(C) a horse of less brightness
(D) More than one of the above
(E) None of the above
Thin black strips will only reduce the intensity of the light but will not cast any shadow as it is quite thin. Hence answer 'C' is correct.
Q 2. Shrillness of sound is determined by
(A) amplitude of sound
(B) wavelength of sound
(C) velocity of sound
(D) More than one of the above
(E) None of the above
It is true that shrillness of sound is determined by its frequency but frequency and wavelength are inversely proportionate. So, it is also true to say that shrillness of sound depends on its wavelength. For example, shorter the wavelength means higher the frequency and more shrill sound. Since frequency and wavelength are inseparably interlinked (velocity= wavelength x frequency and velocity is constant in a medium), the correct answer is 'B'.
Q3. Which of the following photoelectric devices is most suitable for digital applications?
(A) Photovoltaic cell
(B) Photoemitter
(C) Photodiode
(D) More than one of the above
(E) None of the above
Q 4. Ball bearings are used to convert static friction into
(A) drag
(B) sliding friction
(C) rolling friction
(D) More than one of the above
(E) None of the above
Ball bearing are small balls/sphere. In a ball, surface of contact is just a point resulting in very less rolling friction. Hence answer 'C' is correct.
Q 5. A goalkeeper in a game of football pulls his hands backwards after holding the ball shot at the goal. This enables the goalkeeper to
(A) exert large force on the ball
(B) increase the force exerted by the ball on hands
(C) decrease the rate of change of momentum
(D) More than one of the above
(E) None of the above
Q 6. Which among the following is a positively charged particle emitted by a radioactive element?
(A) Beta ray
(B) Alpha ray
(C) Cathode ray
(D) More than one of the above
(E) None of the above
Two protons and two neutrons are bound together to form an alpha particle. High-energy electrons are known as beta particles. Obviously alpha particle is positively charged due to the presence of proton while beta particle is negatively charged due to the presence of electrons. Cathode ray is a stream of electrons leaving the negative electrode (cathode) in a discharge tube containing a gas at low pressure, or electrons emitted by a heated filament in certain electron tubes. It is neither radioactive emission nor positively charged. Hence answer 'B' is correct.
Q 7. Centripetal force is responsible to
(A) keep the body moving along the circular path
(B) fly th object along a straight line
(C) independent motion of the object in space
(D) More than one of the above
(E) None of the above
In a uniform circular motion, though the speed is constant but the direction is changing and as such velocity being a vector quantity, is changing. To change the direction / velocity, force is required which is called centripetal force. For example, if a stone tied to a string is rotated by a person, he has to hold the string tight i.e apply centripetal force otherwise, if he release the string, stone will fly away in the absence of centripetal force. Hence answer 'A' is correct.
Q 8. Which of the following energy changes involves frictional force?
(A) Potential energy to sound energy
(B) Chemical energy to heat energy
(C) Kinetic energy to heat energy
(D) More than one of the above
(E) None of the above
Energy conversion due to friction does not involve change in potential energy / chemical energy. Even when an object is falling in air, its potential energy first gets converted into kinetic energy and then heat or sound etc. In battery, its chemical energy is converted into electrical energy as well as heat but friction has nothing to do in such conversion. Frictional forces apply in a static condition as well as in a moving condition. The respective co-efficient of friction are called static co-efficient and dynamic co-efficient. While in the static condition, there is no displacement i.e. no work done and hence no energy conversion. It is in the dynamic condition, there is movement against the frictional force that there is energy loss by way of heat. In other words, kinetic energy is converted into heat. Correct answer is 'C'.
Q 9. A bus is moving along a straight path and takes sharp turn to the right side suddenly. The passengers sitting in the bus will
(A) fall in the forward direction
(B) bent towards left side
(C) bent towards right side
(D) More than one of the above
(E) None of the above
Q 10. Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the string suitably. By doing so, he / she is adjusting
(A) amplitude of sound
(B) intensity of sound
(C) frequency of the sitar string with the frequency of other musical instruments
(D) More than one of the above
(E) None of the above
String length, diameter, density and tension determines the frequency in which it will vibrate. Since other three are fixed, it is the tension that sitarist tries to adjust to tune its natural frequency. And while playing the Sitar, he changes the effective length of the string by touching the string at different points with his finger. This is how we get different melodious notes (of varying frequency). Amplitude/ intensity of sound is not determined by the tension in the string since it depends on how the Sitarist is playing. Even with a perfectly taut string, he can produce low or very high sound. But he cannot vary its natural frequency and that's why he has to adjust the tension beforehand. So, the correct answer is 'C'.
Q 11. A form of matter has no fixed shape but it has a fixed volume. An example of this form of matter is
(A) krypton
(B) kerosene
(C) carbon steel
(D) More than one of the above
(E) None of the above
Krypton is a gas and kerosene is liquid. While both don’t have fixed form, it is kerosene whose volume cannot be changed significantly with pressure / temperature whereas Krypton being a gas, its volume can be changed drastically with change of pressure / temperature. So, it is kerosene alone which has no fixed form but fixed volume. So the correct answer is 'B'.
Q 12. Some metal oxides react with acid as well as base to produce salt and water. They are known as amphoteric oxides. the examples of amphoteric oxides are
(A) Al2O3 and ZnO
(B) Al2O3 and CuO
(C) CuO and ZnO
(D) More than one of the above
(E) None of the above
Amphoteric oxides have both acidic and basic properties. The oxides of aluminum and zinc are good examples. On the other hand, CuO is basic in nature, it is not amphoteric. Hence answer 'A' is correct.
Q 13. Which gas contribute to global warming through its greenhouse effect?
(A) Nitrous oxide
(B) Methane
(C) Carbon Dioxide
(D) More than one of the above
(E) None of the above
Q 24. Acids react with metal carbonates to liberate ___ gas.
(A) CO2
(B) CO
(C) H2
(D) More than one of the above
(E) None of the above
Q 25. Which acid is described as HOOCCOOH?
(A) Oxalic acid
(B) Acetic acid
(C) Carbonic acid
(D) More than one of the above
(E) None of the above
Q 26. You have been provided with three test tubes. One of them contains distilled water and other two contains an acid solution and a basic solution respectively. Which of them will turn red litmus to blue?
(A) Acid
(B) Base
(C) Distilled water
(D) More than one of the above
(E) None of the above
Q 27. The odour of acetic acid resembles that of
(A) tomato
(B) kerosene
(C) vinegar
(D) More than one of the above
(E) None of the above
Q 28. Why does dry HCl gas
(A) Blue litmus becomes dry in the presence of dry HCl gas.
(B) No H3O+ ions are present. Litmus changes colour only in the presence of H3O+ ions.
(C)
(D) More than one of the above
(E) None of the above
The colour of litmus paper changes in the presence of ions like hydrogen (H+) also and not necessarily hydronium (H3O+) ions only. So option B is wrong. Option A is wrong since litmus paper colour need not be blue to start with. In fact dry HCL gas acts like dehydrating agent that is, it removes water which is crucial for forming hydrogen (H+) or hydronium (H3O+) ions. Hence answer 'B' is correct.
Q 29. Detect the odd one.
(A) Setting of cement
(B) Burning of coal
(C) Ripening of fruit
(D) More than one of the above
(E) None of the above
The correct answer is option 'E'. All are chemical changes and all are also exothermic. So there is no difference. Hence the answer option 'E' is correct.
Q 30. Which of the follwoing statements about diamond and graphit is true?
(A) They have same crystal structure.
(B) They have same degree of hardness.
(C) They have same electrical conductivity.
(D) More than one of the above
(E) None of the above
Diamond and Graphite, both are known as the allotropes of carbon. but neither their crystalline structure nor their hardness are same. Carbon atoms in diamond form three dimensional tetrahedron structure while in graphite it is like hexagonal rings in a plane. Diamond is one of the hardest material while graphite is very soft. Similarly, diamond is poor conductor of electricity whereas graphites are used in the manufacture of electrodes of carbon employed in the electrolytic cells, as it is an excellent conductor of electricity. Hence none of the option is correct and so answer is E.
Q 31. The stomata open or close due to change in the
(A) protein composition of cells
(B) amount of water in cells
(C) position of nucleus in cells
(D) More than one of the above
(E) None of the above
Due to increased transpiration pull during the day, water is absorbed by the roots and transferred through the xylem to various areas of the plant causing the guard cell to swell and become turgid. The stomatal pore is open as a result. The guard cell shrinks and becomes stiff at night because the roots absorb less water. Consequently, stomatal pores close. So the correct option is 'B'.
Q32. Chlorophyll absobs ____ wavelengths of the sunlight.
(A) green and blue
(B) green and red
(C) red and blue
(D) More than one of the above
(E) None of the above
Chlorophyll is a chemical photoreceptor that traps light for photosynthesis in plants. It absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green. Hence answer 'C' is correct.
Q33. Which of the following is not a correct match?
(A) Thick, hard stem with branching near base : Tree
(B) Weak stem which cannot stand upright : Creeper
(C) Petiole : Attaches leaf to stem
(D) More than one of the above
(E) None of the above
Petiole, a part of leaf, attaches leaf to stem by leaf base. It also helps leaf blade to light & allow them to flutter in wind. Creepers are plants with weak soft stem that grow horizontally along with the soil since they cannot stand upright. Trees are tall and big plants having one hard woody stem, the trunk bearing wood branches, leaves and twigs always at some distance from ground, not near the base. Shrubs, on the other hands are plants with woody stem (thick, hard) with branches of almost equal size arising from the stem always above the soil near the base. Option 'B' and 'C' are correctly matched while option 'A' is not correctly matched. Hence option 'A' is the right answer.
Q 34. Water reaches great heights in trees because of suction pull caused by
(A) absorption
(B) transpiration
(C) evaporation
(D) More than one of the above
(E) None of the above
Transpiration is a process that involves loss of water vapour through the stomata of plants. The loss of water vapour from the plant cools the plant down when the weather is very hot, and water from the stem and roots moves upwards or is 'pulled' into the leaves. On the other hand, plants absorb water and minerals from the soil via their roots but water doesnot move upward due to absorption. Similarly, water escapes the tree through evaporation. Hence answer 'B' is correct.
Q 35. Which among the following is a character of chloroplast which makes them qualified to self-replication?
(A) Presence of DNA only
(B) Absence of RNA
(C) Presence of both DNA and RNA
(D) More than one of the above
(E) None of the above
Presence of both DNA & RNA in Chloroplast makes them qualified to self-replication. RNA primers are key to initiating DNA synthesis. They provide the initiation sequence necessary for DNA polymerase to synthesize new strands. So the correct answer is 'C'.
Q 36. The parts of the skeleton that are not as hard as bones and which can be bent are called as
(A) carpals
(B) cartilage
(C) vertebrae
(D) More than one of the above
(E) None of the above
The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. These bones are hard and will break if bent. Cartilage on the other hand, is a strong, flexible connective tissue that protects your joints and bones. Ear is an example of cartilage. Hence answer 'B' is correct.
Q 37. In lichen, a chlorophyll-containing partner, ____ live together.
(A) fungus and a bacterium
(B) alga and a virus
(C) alga and a fungus
(D) More than one of the above
(E) None of the above
Q 38. Female Anopheles can be distinguished from female Culex because it sits
(A) at an anlge with substratum
(B) parallel to the surface of substratum
(C) at right angle to the surface of substratum
(D) More than one of the above
(E) None of the above
The correct answer is option 'A'. At an angle around 45 degree but not right angle /90 degree. Hence the answer option 'A' is correct.
Q 39. The most important cell type associated with the immunity of the body is
(A) platelets
(B) lymphocytes
(C) RBCs
(D) More than one of the above
(E) None of the above
Q 40. Which of the following statements is incorrect about muscles in human body?
(A) Muscles work in pairs.
(B) Muscles becomes shorter, stiffer and thicker when contracted.
(C) Muscles can only push the bone.
(D) More than one of the above
(E) None of the above
Muscles allow a person to move, speak, and chew. They control heartbeat, breathing, and digestion. Other seemingly unrelated functions, including temperature regulation and vision, also rely on the muscular system. Muscles work in pair and become shorter, stiffer and thicker when contracted. So all the options are correct except for 'C'.
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