General Science Quiz Questions & Answers-2

CBSE PHYSICS

1. Why does an electric bulb make a bang when it is broken?
   An electric bulb has a partial vacuum. When it is broken, air rushes into take the place of the vacuum, hence it bangs.
   
2. Why does ship made of steel float though a steel ball sinks?
   The ship displaces more water then its own weight whereas the weight of the water displaced by a steel ball is much less than the weight of the steel ball.
   
3. Why do the stars twinkle?
   The stars seem to twinkle due to two causes. First the light from the stars passes through several mediums; secondly our vision has a tendency to distract.
   
   
4. Why is it easier to swim in a sea than in a river?                                                                         The density of the sea water is higher than the density of the river water.
5. Why is hot soup tastier than the colder one?
   As temperature is increased, surfaced tension decreases and the liquid now occupies more area. Thus the hot soup occupies more area on the tongue and is, therefore, more tasty than the colder one.
6. Thick glass tumblers often crack when very hot liquids are poured into them. Why?
   The inner layer tends to expand more rapidly than the outer layer thus producing phenomenon of unequal expansion resulting in cracks due to the resulting pressure.
7. Why does water get cooled in an earthen pitcher?
   Pitchers have pores through which water percolate which evaporates. During evaporation heat is taken away and the water gets cooled.
8. Why do the sky and the water of the ocean look blue?
   The blue part of the sunlight is scattered by the particles of the atmosphere around, while other parts of light pass through it: that is why the sky looks blue because of the refraction of the blue light only.
9. Which will reach the ground first: a bullet which is shot horizontally from a gun or similar bullet thrown upward from the ground?
   Obviously horizontally shot bullet is to come down first. Its direction is perpendicular to that of gravitational force. So both vectors will not affect each other but in the case of a bullet shot upward has velocity vector in the opposite direction of gravitation force. So it will take more time.
10. Why does an iron gain weight on rusting?
    The rusted iron is nothing but iron-oxide. Iron in the presence of moisture absorbs oxygen from the atmosphere and forms iron oxide. The weight gained is equal to the weight of oxygen absorbed.
    
11. Why does hard water not readily form lather with soap?
    Hard water contains the sulphates and chlorides of magnesium and calcium, which form insoluble compounds with soap. Hence soap does not lather with hard water.
12. Why tare mountains cooler than plains?
    It is so because, firstly, the air on the mountains is rare than that on the plains and absorbs less heat than the air on the plains, secondly the heat absorbed during the day on the mountains radiates away more quickly due to the rarity of the air, thirdly, major portion of the mountains remains in shade.
13. Why is sea-water saline?
    The rivers in the course of their flow and falling into the sea bring with them deposits of salt this process has been going on for lakhs of years, it makes sea-water saline.
14. Glass when heated cracks while metal does not?
    Glass being bad conductor of heat only that part is heated which comes into contact with heat while the other parts remain unaffected. This results in unequal expansion and hence the tension which cracks the glass. On the other hand, metal is a good conductor of heat and so all its bulk gets uniformly heated and hence no surface tension.
15. Why does it not hurt when we cut our nails?
    Nails are the parts of the body which are not connected either with the blood vessels or cartilage and hence having no relation with the nervous system. Therefore cutting them does not give pain.
    
    
16. A hydrogen balloon rises. Why?
    Hydrogen is lighter than air; the weight of the hydrogen balloon is less than the weight of the air displaced by it.
    
17. Why is a compass used as an indicator of direction?
    The magnetic needle of the compass due to the influence of the earth’s magnetic field always lies in the north south direction. Hence we can know the direction.
    
18. Why is a country like Ladakh, it may be very hot in sunshine, but bitterly cold in shade?
    The atmosphere on great heights like Ladakh is rarefied, which offers little obstacle to the rays of the sun which are therefore, scorching. But the rarefied air absorbs little heat from the rays of the sun; therefore, the atmosphere remains cold. Hence it is very cold in the shade.
    
19. Why does a straight stick look bent when a part of it is immersed in water?
    The rays of the lights passing from a rare medium to a dense medium change their course due to refraction, where the rays coming from stick in water come in air at surface they get displaced away from perpendicular as our eyes see straight way so the stick seems bent.
    
20. Why does water boil at a lower temperature on the hills than on the plains?
    The higher the pressure, the higher boiling point: the lower the pressure the lower the boiling point. The atmosphere pressure on the hills is lower than that on the earth.