scientific reasoning 38 important gk question
scientific reasoning important gk question —-
Blotting paper absorbs ink.Why ?–scientific reasoning
The blotting paper is porous and has a number of capillaries of very fine pores.When a portion of the blotting paper is brought in contact with the ink, it enters the capillaries due to the surface tension.
Why does carbon dioxide is used in extinguishing fire?
Carbon dioxide being heavier than oxygen acts as fire extinguisher by cutting off its oxygen supply to a burning object.
Why do the stars twinkle ?
Stars appear to twinkle because its light travels through different layers of space of varying densities. As a result the light from the stars bends and makes them appear to blink on and off.
Why is it not possible to see the stars in the day light ?—scientific reasoning
The blazing light of the sun during daytime prevents the less intense light of the stars from being seen distinctly.
Why does the ice float on water while it sinks in alcohol?
The specific gravity of ice is less than that of water but the same is more than that of alcohol, hence ice floats on water but sinks in alcohol.
Why is mercury used in thermometer ?
Mercury is the only metal which is in liquid state even at the ordinary room tempe rature. Also, it uniformly expands when heated and does not stick to the walls of thermometer. Its high boiling point and low freezing point is the main reason for using it in ordinary thermometers.
How can bats fly in the dark avoiding obstacles?
The ultrasonic waves produced by bats during flying are reflected back when they hit the obstacles. Hence, bats can find their path without any difficulty.
Why does water pipe often burst in cold countries?
In winter, the water in the pipes freezes. On freezing into ice the water increases in volume, which results in bursting of water pipes.
Why is cooking quicker in pressure cooker ?
In a pressure cooker, boiling point of water is raised by increasing pressure with steam. Food gets high temperature and so cooking becomes quicker.
We bring our hands close to mouth while shouting to somebody at a distance. Why?—scientific reasoning
By bringing the hands close to our mouth, the sound energy is not allowed to spread in all directions, rather being made unidirectional(i.e. directed in a particular direction). Hence the sound produced becomes louder.
Why do we lean forward while climbing a hill ?
Leaning forward enables us to keep the line passing through the centre of gravity vertically downward, within our feet, and thus the equilibrium is kept stable.
Why are lightning conductors fixed at the top of high buildings ?
When an electric discharge takes place from the cloud, the lightning conductor provides it an easy conducting path to the earth without damaging the building.
- Why does a parachute must have a hole ?
A hole in the centre of parachute is made to avoid oscillation of the parachute while descending owing to the changing currents of wind. The hole allows the air to run out of the parachute regularly.
How does a flute produce different sound notes?
A flute produces different sound notes because air particles passing through it are vibrated with different frequencies with the closing and opening of the holes.
Why do we use a fuse in an electric circuit?
A fuse is used in an electric circuit because when excess current flows through the circuit the fuse melts and breaks the circuit and prevents the damage to any of the electrical goods used.
What causes wind ?
Winds are caused by the unequal heating of the earth’s surface and rotation of earth.
Why does a drop of liquid assume a spherical shape ?—scientific reasoning
A drop of liquid assumes a spherical shape due to surface tension. A sphere has the least surface area for a given volume.
What is a breeder reactor ?
A breeder reactor is such a reactor which produces more fissionable material than it burns.
What does a moderator do in a nuclear reactor?
The number of nuclei split by the impact of neutrons is regulated by a moderator in a nuclear reactor.
Why is a small space left at the joint between the two rails?
To permit the expansion of rails due to heat generated by friction of the moving train in summer.
A glass tumbler is filled to the brim with water and a piece of ice is floating on it. As the ice melts, will the wateroverflow or not? Give reason for your answer.
Level of water remains unchanged because the volume of water produced by the melting of ice is exactly the same as that of the piece of ice. On melting, the water will be equal to the volume of water displaced by the ice.
When a moving train slows down quickly, will a passenger tend to fall backward orforward? Explain why?
The passenger will tend to fall forward because the lower portion of his body which is in contact with the seat will come to rest quickly whereas the upper portion of the body continues to be in a state of motion. Hence, the person is thrown forward, due to inertia.
Explain why it takes more time to cook meat and vegetables at hill stations?
At higher altitudes, the atmospheric pressure is low as compared to that in the plains and, therefore water boils below 1000C. Hence sufficient heat is not supplied for cooking the meat and vegetables at hill stations.
When we drink soft drinks through a straw, why does the liquid go up into our mouth?—scientific reasoning
When a person sucks air from the straw, the pressure of the air inside the straw is reduced as compared to the atmospheric pressure acting on the surface of the liquid. Therefore, the soft drink rushes up into the straw and to the mouth.
Explain why the moisture (water droplets) gathers on the outer side of a glass tumbler containing ice-cold water?
The water vapour present in air gets cooled and appear as droplets of water on coming in contact with the cold surface of the glass tumbler.
Why does a metal seen colder in winter and hotter in summer compared with a piece of wood?
Metals absorb and transmit heat more rapidly than wood.
A thick glass tumbler often cracks when a very hot liquid is poured in it. Why?—scientific reasoning
The inner surface of the thick glass tumbler coming in contact with the hot liquid expands more in comparison to the outer surface which is relatively at a lower temperature. The uneven expansion of inner and outer surface may produce cracks.
How does a rainbow form?
Explain the phenomenon. After rain, some clouds continue to linger in the sky and they contain water droplets. Water droplets act like prisms. Sun’s rays falling on water droplets suffer dispersion and produce a spectrum. The different colours are viewed in the form of a rainbow.
What causes the rumbling sound of thunder?
Air is heated instantly whenan electrical charge of lightning passes through it. The heat causes the molecules of air to expand in all the directions. As the molecules seek more room, they collide violently with layers of cool air, and set up a great air wave that has the sound of thunder.
Why are mornings and evenings less warm than noon?
In the mornings and evenings, the rays of the sun falling on earth are slanting and their distance is more.The earth gets heated up only slightly. At noon, the rays of the sun falling on the earth are nearly vertical and the distance is also less, with the result that the earth gets heated up considerably.Hence mornings and evenings are less warm than noon.
The sky appears blue. Give reason.
Violet and blue light have short wavelength and are scattered more than red light waves.While red light goes almost straight through the atmosphere,blue and violet are scattered by particles in the atmosphere.Thus we see a blue sky.
What is the difference between a planet and a star?
Stars are self-luminous celestial bodies and they have a system of their own. Planets, on the other hand, are bodies which revolve around a star and shine by the reflected light of the stars.
What is the difference between supersonic and ultrasonic sounds?
Sounds of frequency higher than 20,000 Hz are known as ultrasonic and are inaudible.The speed greater than the speed of sound is referred to as supersonic.
Copper wire cannot be used as a heating element in electric heaters. Why?
Copper has less melting point and if we use it in electric heater it cannot withstand high temperature.
What would happen if the force of gravity were to disappear suddenly ?
In the absence of gravitational force, all living objects on the earth will be practically in a floating condition. They will be thrown away because of the centrifugal force caused by the rotation of earth. After a certain time the whole earth will disintegrate.
Radio reception improves slightly during the night.Why?
During day time due to sunlight the radio broadcasting is affected to a certain extend. Due to the absence of sun during night radio reception improves slightly.
We perspire on a hot day. why?
Human body is physiologically conditioned to maintain in form the temperature. When the heat produced in the body becomes excessive and not dissipated properly,the sweat glands inside the body are stimulated to secrete sweat. Therefore, we perspire on a hot day.
The gun kicks back when a bullet is fired. Why?
According to Newton’s third law of motion, to every action, there is an equal and opposite reaction. So the gun kicks back when a bullet is fired.
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