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what is the difference between sound wave and light wave ?

Posted by Krati Chaturvedi (Feb 17, 2017 8:54 p.m.) (Question ID: 2266)

  • Answers:
  • The difference between Sound waves and Light Waves are: Sound Waves require a medium where Light Waves do not require a medium

    <h3>Sound Waves</h3>

    1. Require a medium.

    2. Travel with a speed of 332 m/s at 0 C.

    3. Are longitudinal waves consisting of compressions and rarefactions.

    4. Are of different frequencies, giving notes of different pitches.

    5. Do not travel far as their energy is dissipated easily.

    <h3>Light Waves</h3>

    1. Do not require a medium

    2. Travel with a speed of 3 *10m/s.

    3. Are electromagnetic waves consisting of varying electric and magnetic fields.

    4. Are of different frequencies, resulting in different colors.

    5. Can travel through a much greater distance.

    Answered by imran khan (Feb 17, 2017 9:54 p.m.)
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Can anyone provide me some analytical questions for the chapter Air and Water pollution ?

Posted by Akanksha Arora (Feb 11, 2017 3:19 p.m.) (Question ID: 2014)

  • Answers:
  • Question 1:

    What are the different ways in which water gets contaminated?

    Answer :

    Water gets contaminated by the addition of:
    (i) Agricultural chemicals: Farmers use excessive amounts of pesticides and fertilizers to increase crop production. These chemicals get carried away to the water bodies due to rains and floods which lead to water pollution.
    (ii) Industrial wastes: Industries release harmful chemical wastes into water sources, thereby polluting them.
    (iii) Sewage wastes: Waste materials from kitchens, toilets, and laundry sources are also responsible for contaminating water.

    <h1> </h1>

    Question 2:

    At an individual level, how can you help reduce air pollution?

    Answer :

    An individual can reduce air pollution by:
    (i) Avoiding the use of cars as much as possible and by using public transport whenever possible.
    (ii) By not using vehicles for short distances. 
    (iii) By using clean fuels such as LPG and CNG instead of diesel and petrol.
    (iv) Always disposing the garbage properly and not burning it.
    (v) Controlling the emissions from vehicles and household chimneys.

    Question 3:

    Clear, transparent water is always fit for drinking. Comment.

    Answer :

    No. Clear and transparent water is not always fit for drinking. Water might appear clean, but it may contain some disease causing micro-organisms and other dissolved impurities. Hence, it is advised to purify water before drinking. Purification can be done by water purifying systems or by boiling the water.

    Question 4:

    You are a member of the municipal body of your town.
    Make a list of measures that would help your town to ensure the supply of clean water to all its residents.

    Answer :

    To ensure the supply of clean water to all residents the following steps must be taken:
    (i) The main water source must be built in clean surroundings and should be maintained properly.
    (ii) Chemical methods such as chlorination must be used for purifying water.
    (iii) The area around water pipes must also be clean.


    Question 5:

    Explain the differences between pure air and polluted air.

    Answer :

    Pure air contains around 78% nitrogen, 21% oxygen, and 0.03% carbon dioxide. Other gases such as argon, methane, ozone, and water vapours are also present in small quantities. When this composition of air is altered by the addition of harmful substances or gases such as nitrogen dioxide, sulphur dioxide, carbon monoxide, and particulate matter, then the air is said to be polluted.

    Question 6:

    Explain circumstances leading to acid rain. How does acid rain affect us?

    Answer :

    Burning of fossil fuels such as coal and diesel releases a variety of pollutants such as sulphur dioxide and nitrogen dioxide into the atmosphere. These pollutants react with water vapours present in the atmosphere to form sulphuric acid and nitric acid respectively. These acids come down with the rain, thereby resulting in acid rain.
    Effects of acid rain: 
    (i) Acid rains damage crops. 
    (ii) Acid rains corrode buildings and structures especially those made of marble such as Taj Mahal.

    Question 7:

    Which of the following is not a greenhouse gas?
    (a) Carbon dioxide
    (b) Sulphur dioxide
    (c) Methane
    (d) Nitrogen

    Answer :

    (d) Nitrogen


    Question 8:

    Describe the ‘Greenhouse Effect’ in your own words.

    Answer :

    Greenhouse effect may lead to global warming, i.e., an overall increase in the average temperature of the Earth. Greenhouse effect is caused by greenhouse gases. Examples of greenhouse gases include carbon dioxide, methane, and water vapour. When solar radiations reach the Earth, some of these radiations are absorbed by earth and then released back to the atmosphere. Greenhouse gases present in the atmosphere trap these radiations and do not allow heat to leave. This helps in keeping our planet warm and thus, helps in human survival. However, an indiscriminate increase in the amount of greenhouse gases can lead to excessive increase in the Earth’s temperature leading to global warming.

    <h1> </h1>

    Question 9:

    Prepare a brief speech on global warming. You have to deliver the speech in your class.

    Answer :

    Global warming is an increase in the average temperature of the Earth’s surface. It occurs as a result of an increased concentration of greenhouse gases in the atmosphere. The greenhouse gases include carbon dioxide, methane, and water vapour. These gases trap solar radiations released back by the Earth. This helps in keeping our planet warm and thus, helps in human survival. However, an increase in the amount of greenhouse gases can lead to an increase in the Earth’s temperature leading to global warming.

    Question 10:

    Describe the threat to the beauty of the Taj Mahal.

    Answer :

    Acid rain is a major threat to the beauty of the Taj Mahal. When acid rains fall on the monument (that is completely made of marble), they react with marble to form a powder-like substance that is then washed away by the rain. This phenomenon is known as marble cancer. Also, the soot particles emitted from the Mathura oil refinery located near Agra is leading to the yellowing of the marble. 

    Question 11:

    Why does the increased level of nutrients in the water affect the survival of aquatic organisms?

    Answered by imran khan (Feb 11, 2017 3:28 p.m.)
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Mercury has day in one part and night in other part.Give reason?

Posted by Nageswara Rao (Feb 09, 2017 2:39 p.m.) (Question ID: 1949)

  • plz answer its my hw.......i am not able to ans..:(


    Posted by Nageswara Rao (Feb 09, 2017 2:51 p.m.)
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  • Answers:

    On Mercury temperatures can get as hot as 430 degrees Celsius during the day and as cold as -180 degrees Celsius at night.
    Mercury is the planet in our solar system that sits closest to the sun. The distance between Mercury and the sun ranges from 46 million kilometers to 69.8 million kilometers. The earth sits at a comfy 150 million kilometers. This is one reason why it gets so hot on Mercury during the day.

    The other reason is that Mercury has a very thin and unstable atmosphere. At a size about a third of the earth and with a mass (what we on earth see as ‘weight’) that is 0.05 times as much as the earth, Mercury just doesn’t have the gravity to keep gases trapped around it, creating an atmosphere. Due to the high temperature, solar winds, and the low gravity (about a third of earth’s gravity), gases keep escaping the planet, quite literally just blowing away.
    Atmospheres can trap heat, that’s why it can still be nice and warm at night here on earth.
    Mercury’s atmosphere is too thin, unstable and close to the sun to make any notable difference in the temperature.

    Space is cold. Space is very cold. So cold in fact, that it can almost reach absolute zero, the point where molecules stop moving (and they always move). In space, the coldest temperature you can get is 2.7 Kelvin, about -270 degrees Celsius.
    Sunlight reflected from other planets and moons, gases that move through space, the very thin atmosphere and the surface of Mercury itself are the main reasons that temperatures on Mercury don’t get lower than about -180 °C at night

    Answered by imran khan (Feb 09, 2017 8:22 p.m.)
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Why water comes only on our earth and not comes on other planets?



Posted by Abhishek Kumar (Feb 08, 2017 9:37 p.m.) (Question ID: 1928)

  • Answers:
  • The water that makes Earth a majestic blue marble was here from the time of our planet's birth, according to a <a href="">new study of ancient meteorites</a>, scientists reported Thursday.

    Where do the oceans come from? The study headed by <a href="">Adam Sarafian</a> of the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts, found that our seas may have arrived much earlier on our planet than previously thought.

    The study pushes back the clock on the origin of Earth's water by hundreds of millions of years, to around 4.6 billion years ago, when all the worlds of the inner solar system were still forming.

    Scientists had suspected that our planet formed dry, with high-energy impacts creating a molten surface on the infant Earth. Water came much later, went the thinking, thanks to collisions with wet comets and asteroids.

    "Some people have argued that any water molecules that were present as the planets were forming would have evaporated or been blown off into space," said study co-author <a href="">Horst Marschall</a>, a geologist at WHOI.

    For that reason, he said, scientists thought that "surface water as it exists on our planet today must have come much, much later—hundreds of millions of years later."

    Answered by imran khan (Feb 09, 2017 8:25 p.m.)
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What happens when reflection by a plane, polished surface is 

Posted by Praveen Chetalla (Jan 28, 2017 7:03 p.m.) (Question ID: 1654)

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  • When a rays of light reflected by a plane mirror image formation takes place.


    Answered by RAJENDRA SINGH (Jan 28, 2017 7:40 p.m.)
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What is bitumen?


Posted by Irfan Alam (Jan 27, 2017 5:08 p.m.) (Question ID: 1633)

  • Answers:
  • Ans. Bitumen is a mixture of Organic Liquids that are highly Viscous, Black, Sticky, Entirely Soluble in Carbon Disulfide, and composed primarily of highly condensed Polycyclic Aromatic Hydrocarbons.

    Naturally occurring or crude bitumen is a sticky, tar-like form of petroleum which is so thick and heavy that it must be heated or diluted before it will flow. At room temperature, it is much like cold molasses.

    Answered by Naveen Sharma (Jan 27, 2017 5:23 p.m.)
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Is it the same side of the moon that always faces the earth?

Posted by Tanya Gaur (Jan 22, 2017 11:19 a.m.) (Question ID: 1541)

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  • Ans, Though the moon does rotate around its axis, the speed with which it completes these revolutions match the amount of time it takes to orbit around the Earth, leading the same side to be faced toward Earth at all times. This process takes a about month, meaning the moon's days are as long as an Earth month

    Answered by Payal Singh (Jan 23, 2017 1:44 p.m.)
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  • If the Moon didn't spin at all, then eventually it would show its far side to the Earthwhile moving around our planet in orbit. However, since the rotational period is exactly the same as the orbital period, the same portion of the Moon's sphere is always facing the Earth


    Answered by rosy 12 (Jan 22, 2017 12:28 p.m.)
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Posted by Anil Gupta (Jan 22, 2017 9:25 a.m.) (Question ID: 1536)

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  • The land is colder than the nearby water due to its lower specific heat. The cold land cools the air above it. ... Winds called landbreezes blow from the high to the low pressure cell. These local winds blow from the cooler land to the warmer ocean.

    Answered by Vikrant Singh (Jan 22, 2017 7:40 p.m.)
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Describe the threat to the beauty of Taj Mahal ?

Posted by ishraque Haider (Jan 16, 2017 8:34 p.m.) (Question ID: 1412)

  • Answers:
  • Acid rain is a major threat to the beauty of the Taj Mahal. When acid rains fall on themonument (that is completely made of marble), they react with marble to form a powderlike substance that is then washed away by the rain. This phenomenon is known as marble cancer. Also, the soot particles emitted from the Mathura oil refinery located near Agra is leading to the yellowing of the marble.

    Answered by Payal Singh (Jan 17, 2017 3:52 p.m.)
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  • Taj Mahal is made up of white marble. Marble is composed of calcium carbonate. Calcium carbonate reacts with acids and thus gets corroded. This is the reason; acid rain is damaging the Taj Mahal. This wonderful monument does not look white but is looking pale and dull. If corrective measures are not taken, the future generations may not be able to see the beauty of the Taj.

    Answered by Naveen Sharma (Jan 17, 2017 7:10 a.m.)
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define water polluntant

Posted by ujwal singh (Jan 12, 2017 6:12 a.m.) (Question ID: 1301)

  • Answers:
  • Water pollution is an appalling problem, powerful enough to lead the world on a path of destruction. Water is an easy solvent, enabling most pollutants to dissolve in it easily and contaminate it. The most basic effect of water pollution is directly suffered by the organisms and vegetation that survive in water, including amphibians. On a human level, several people die each day due to consumption of polluted and infected water.

    Water pollutant:

    1. Industrial waste
    2. Sewage and waste water
    3. Mining activities
    4. Marine dumping
    5. Accidental Oil leakage:
    6. Burning of fossil fuels
    7. Chemical fertilizers and pesticides
    8. Leakage from sewer lines
    9. Radioactive waste
    10. Animal waste
    Answered by Payal Singh (Jan 12, 2017 12:16 p.m.)
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what are the diferent ways in which water gets contaminated

Posted by ujwal singh (Jan 12, 2017 6:10 a.m.) (Question ID: 1300)

  • Answers:
  • Though water pollution may occur from a variety of sources, there are two terms used to describe how the water became polluted.

    When water is polluted from point sources, this is pollution from a discrete location. This discrete location could be a factory, a sewer pipe or a runoff from a single farm. The BP oil spill in 2010 is an example of point source pollution, because the massive amount of oil leaked from a single point of origin.

    Water pollution may also be from non-point source pollution, which is when several points of contamination over a large area contribute to the pollution of a water body. For example, one water body may be contaminated by multiple sources like agricultural runoff, city street runoff, construction sites and residential lawns. The Mississippi River is at great risk for non-point source pollution because it is so large and is exposed to a variety of possible pollution sources.

    Answered by Naveen Sharma (Jan 12, 2017 12:02 p.m.)
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What is fertilization in human?

Posted by RUDRA PRATAP SINGH CHOTU (Jan 10, 2017 10:06 a.m.) (Question ID: 1238)

  • Answers:
  • Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the fallopian tube. The result of this union is the production of a zygote cell, or fertilized egg, initiating prenatal development.

    Answered by Manish Gandhi (Jan 10, 2017 11:48 a.m.)
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what is the shape of our galxy the milkey way


Posted by anil pandey (Jan 08, 2017 8:12 p.m.) (Question ID: 1193)

  • Answers:
  • The shape of our galaxy milky way is barred spiral galaxy in which the central elliptical buldge of closely packed starts lying in the direction of Sagittarius.

    Answered by shruti dadhwal (Jan 08, 2017 11:31 p.m.)
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how are cells classified


Posted by madhumita reddy (Dec 28, 2016 3:10 p.m.) (Question ID: 907)

  • Answers:
  • Mainly there are two types of cells which are Eukaryotic and Prokaryotic. 

    The Prokaryotic cells do not have a well defined nuclear membrane. Eg blue green algae and bacteria. 

    The Eukaryotic cells have a well defined nuclear membrane. Example human beings. 


    On the basis of shape we have round cells,  elongated cells and branched cells. 

    For example nerve cell is the longest and branched cell in a human body so that it can transmit the messages rapidly. 

    Answered by Shweta Gulati (Dec 31, 2016 12:41 a.m.)
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  • Cells are classified into two categories,

    1) prokaryotic cells

    2)Eukaryotic cells


    Answered by Leena Burman (Dec 29, 2016 1:36 p.m.)
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what is eutrophication?

what is hydrophobic?

Posted by mothiswar balasankar (Dec 23, 2016 7:21 p.m.) (Question ID: 811)

  • Answers:
  • Eutrophication is enrichment of ecosystem with chemical nutrients mostly by compounds of Nitrogen and Phosphorus is called Eutrophication.It results in growth of algae in water and deteriorates the water quality.

    Hydrophobic- hydro+phobic 

    Hydro means water and phobic means hating or repelling

    So it is the property of molecule which is water repelling in nature.They are non polar in nature and do not mix with water.for example oil,greese etc 

    Answered by shruti dadhwal (Dec 24, 2016 4:18 a.m.)
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  1. When you fly in an aeroplane we say that every door or window should be closed as there is very less oxygen but when we fly in a helicopter we are opening the doors. Can you find the reason for it? How do we get oxygen to breath when we fly in a helicopter?
Posted by NAVABHAARATHI ASOKAN (Dec 20, 2016 9:53 p.m.) (Question ID: 789)

  • Answers:
  • Aeroplane flys at much higher altitude than the helicopter. Therefore the decrese in air pressure in case of aeroplne is much more than helicopter at which they fly. Now we all know that inside the aeroplane we need to maintain the atmospheric pressure to keep all our biological systems properly. so an equillibrium of pressure is maintained there. if the doors and windows are opened that equillibrium will be disturbed and hence the situation can be fatal.

    Since Helicopter can rise only upto a certain level where the air density is lower but not fatal for us so no air pressure equillibrium is maintained. Therefore the doors and windows can be open

    Moreover drag caused by the air is much more in case of aeroplane than helicopter because the former runs in much faster speed than latter. This drag also hamper the functioning of the system of an aeroplane. so the windows are closed. Since the drag in case of helicopter is not much so it doesnot affect the working of a helicopter.

    Answered by Amrita Mukherjee (Jan 18, 2017 6:56 p.m.)
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How is embryo different from a foetus?

Posted by Anant Kumar (Dec 19, 2016 11 a.m.) (Question ID: 777)

  • Answers:
  • An embryo is multicellular diploid eukaryote in it earliest stage of development.At the end of 8 weeks in humans, the embryonic stage is over and the fetel stage begins.

    Answered by shruti dadhwal (Dec 19, 2016 7:17 p.m.)
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  • Foetus is the last stage of baby's development while embryo is the first stage.

    Foetus is fully developed and clearly identical as a baby while embryo is just the division's start of a baby and not clearly identical.

    Foetus occurs after embryo and embryo before foetus.

    Embryo is the combination of just two cells while foetus is almost a complete baby.

    Answered by Devanshu Agarwal (Dec 19, 2016 4:27 p.m.)
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Posted by SHEETAL MALL (Dec 16, 2016 8:08 p.m.) (Question ID: 765)

  • Answers:
  • A microorganism is an organism that is so small to be seen by nakrd eye and are visible by an instrument called microscope.They can be unicellular or multicellular organisms.

    Answered by shruti dadhwal (Dec 18, 2016 10:27 p.m.)
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  • A microorganism or microbe is an organism which is too small to be seen by the unaided human eye. They are microscopic.

    The study of microorganisms is called microbiology.

    Microorganisms include bacteria, fungi, archaea or protists and viruses.

    Answered by Naveen Sharma (Dec 17, 2016 10:06 a.m.)
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my question is why light get dispersed in a glass prism

Posted by Sarthak V Vats (Nov 26, 2016 7:10 a.m.) (Question ID: 635)

  • Answers:
  • When a light ray enters into a denser medium from a rarer medium it bends away from the normal at the interface of the two medium because of the decrease in the velocity. Light rays with longer wavelenth bends the least and with sorter wavelength bends the most. Now we all know the white light has seven component light rays of different colours. All of them vary with respective to their wavelength. Red has the longest wavelenth whereas the violet has the shortest. Therefore when a white light enters into the prism all the component light rays bends away from the normal inversely proportional to their wavelength.e.g. red light bends the least and violet bends the most. Therefore we get a spectrum of seven different colours.  

    Answered by Amrita Mukherjee (Dec 08, 2016 1:03 p.m.)
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  • its simple because every colour of light have diffrent velocity and wavelength.So,when a white light enters the prism the light with large wavelength(red) bends the least and colour light with smallest wavelength(violet) bends the the most and similarly it happens for all the colour of light.and we can see all the diffreny colour of white light.

    Answered by anuranjan vatsalya (Nov 26, 2016 2:44 p.m.)
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what is the common name for the formula N2

Posted by Rishabh Narayan (Nov 22, 2016 8:43 p.m.) (Question ID: 620)

  • Answers:
  • The molecule N2 is called nitrogen molecule.

    Answered by shruti dadhwal (Dec 06, 2016 8:10 p.m.)
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  • Common name for the formula N2 is Nitrogen molecule.

    Answered by RAJENDRA SINGH (Nov 22, 2016 10:06 p.m.)
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How is cloning of dolly done


Posted by Abhishek Varma Mandapati (Nov 21, 2016 8:32 p.m.) (Question ID: 613)

  • Answers:
  • Dolly sheep was the first mammal clone. It was created by a process called nuclear transfer from a somatic cell (body cell). In this process from the body of a healthy individual some somatic cells are collected. In case of Dolly the nucleus was collected from the mammary gland of a feamale sheep. Then this nucleus is placed inside an unfertilized oocyte whose nucleus ia already removed. After this hybridization completed successfully this hybrid cell is stimulated for cell division (by giving an electric shock) and once it has attain the blastocyst phase it is implanted in the surrogate mother sheep. In case of Dolly she had three mothers. One has given the genetic material (the nucleus), second on has given the oocyte and third one is the surrogate mother.

    Answered by Amrita Mukherjee (Dec 08, 2016 1:27 p.m.)
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asiatic lions and tigers are endangered species. how do we justify this answer?

Posted by Chandini .V.Nair (Nov 12, 2016 1:39 p.m.) (Question ID: 531)

  • Answers:
    • The Asiatic lion is endangered largely because of hunting by humans after firearms became widespread.  Its numbers are slowly recovering, having risen from merely 100 animals to about 200 today, according to Bristol Zoo Gardens.
    • Tigers are endangered because of climate change, loss of habitat and poaching. Most of the reasons tigers are on the endangered species list are tied to human interference. The overall combined population of all five tiger species is between 3,000 and 5,000, according to National Geographic.                                                                             due to population loss and several inhuman activities they are endangered
    • hope its helpful:)
    Answered by Avanthika Sriram (Nov 12, 2016 4:06 p.m.)
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how does a red list differ from red data book?

Posted by Chandini .V.Nair (Nov 12, 2016 1:35 p.m.) (Question ID: 530)

  • Answers:
  • Red List:

    • The IUCN (International union for conservation of nature) Red list is the most authentic study of the global conservation status for the threatened biological species.
    • The IUCN Red List is set upon criteria to evaluate the risk of being extinct of thousands of species and subspecies. These criteria are relevant to all species and all regions of the world.

    Red Data Book:

    • The Red data bool is the state document maintained for documenting the details rare and endengered species of plant animal fungi upto the level of sub species exist within the area of the state or country.
    • This provides information about studies and monitoring programmes on rare and endengered species and their habitat. 
    Answered by Amrita Mukherjee (Dec 08, 2016 3:40 p.m.)
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what is extinct

Posted by Jaiprakash Singh (Nov 06, 2016 8 p.m.) (Question ID: 492)

  • Answers:
  • Extinct means the one which does not exist presently but they existed in the past.For example, Diana sores are extinct species.

    Answered by shruti dadhwal (Dec 06, 2016 8:12 p.m.)
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  • anything which existed in a particular environment but now is not found or available.

    Answered by Radha Jittu (Nov 06, 2016 10:16 p.m.)
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what is cultivation

Posted by rohit jatav (Nov 01, 2016 2:11 p.m.) (Question ID: 472)

  • Answers:
  • Cultivation of crops involves several activities undertaken by a farmer over a period of time which are referred to as agricultural pratices. They are sequentially as follows:

    1. Preparation of soil
    2. Sowing
    3. Adding manure and fertilisers
    4. Irrigation
    5. Protecting from weeds
    6. Harvesting
    7. Storage
    Answered by Amrita Mukherjee (Dec 08, 2016 3:48 p.m.)
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  • Cultivation is the process of production of plants giving them proper nutrients, environment, water etc and taking their care .

    Answered by shruti dadhwal (Dec 06, 2016 10:29 p.m.)
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what is the difference between atmospheric  pressure and vaccum?


Posted by Pranjal Gupta (Oct 21, 2016 8:11 a.m.) (Question ID: 437)

  • Answers:
  • The atmospheric pressure is the pressure that an area experiences due to the force exerted by the atmosphere.

    Vacuum is ideally an area which is devoid of any matter that means in vacuum the atmospheric pressure is zero. 

    vacuum pressure is measured as the difference between atmospheric pressure and absolute pressure. (Absolute pressuer : actual pressure at given position)

    Answered by Amrita Mukherjee (Dec 08, 2016 4:10 p.m.)
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  • Vaccuum is the region where pressure is zero and even the sound cannot propagate in vaccuum .The atmospheric pressure is the pressure exerted by the air at sea level and it is taken as 1 atm as standard value.

    Answered by shruti dadhwal (Dec 06, 2016 8:14 p.m.)
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  • Vacuum, is a region without any matter, or a region of zero pressure (perfect vacuum). It is practically impossible to create perfect vacuum. So real vacuum should actually be defined as a region <i>almost </i>devoid of matter, or of very low pressure.

    Vaccum is a non-existent word. It is just a spelling mistake of the former. Other common spelling mistakes made in writing vacuum are <i>vacume, vacum, vaacum, vaccuum</i>

    Answered by Pappu Choudhary (Oct 23, 2016 10:27 p.m.)
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  • Absolute pressure : is zero-referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. Gauge pressure : is zero-referenced against ambient air pressure, so it is equal to absolute pressure minusatmospheric pressure. Negative signs are usually omitted.


    Answered by Kashish Gupta (Oct 21, 2016 9:25 a.m.)
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why friction is needed ?

Posted by Pranjal Gupta (Oct 20, 2016 4:54 p.m.) (Question ID: 432)

  • Answers:
  • Friction is required for us to move.we cannot move if there is no friction.we cannot move in a frictionles surface. When we move forward , there is a force which opposes it an it is called friction.

    Answered by shruti dadhwal (Dec 06, 2016 8:17 p.m.)
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  • Friction is a necessary evil . It is needed for the motion of any object over the other . 

    Answered by Meghan Wizard (Oct 23, 2016 11:14 p.m.)
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  • Friction is essential for movement of vehicles, locomotion in our body and a number of other actitivies.

    Answered by RAJENDRA SINGH (Oct 21, 2016 10:16 a.m.)
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Q.1 you are provided with two similar bars , one is a bar magnrt and the other is a soft iron bar . how will you distinguish between them without the use of any other magnet or bar? answer related to geographic north south direction.

Posted by kumar (Oct 13, 2016 2:56 p.m.) (Question ID: 378)

  • Answers:
  • When both the rods are suspended using a thread, the bar magnet always setttle in north- south direction as as itself  acts as huge magnet having north pole towards geographical south. the soft iron bar may settle in any direction,

    Answered by RAJENDRA SINGH (Oct 14, 2016 7:33 p.m.)
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Posted by Manya Gupta (Sep 28, 2016 12:25 p.m.) (Question ID: 315)

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  • The function of nucleus in the cell are :

    1. It carries genes and helps in inheritance of of character from parents to progeny.
    2. It also the metabolic activity of the cells
    3. it is refered as the brain of the cell
    Answered by Amrita Mukherjee (Dec 08, 2016 4:20 p.m.)
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  • The nucleus is a membrane-enclosed organelle found in eukaryotic cells.

    The function of a nucleus is to control all activities of a cell. It controls gene expression and mediate the replication of DNA during the cell cycle.

    Answered by Rashmi Bajpayee (Sep 28, 2016 7:36 p.m.)
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