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A mole is quite often called chemist's dozen.Explain.

Posted by Debaditya Ghosh (Feb 22, 2017 11:06 a.m.) (Question ID: 2437)

  • Answers:
  • Ans. A dozen is a common counting unit. A counting unit is a convenient number that makes it easier to count objects. We ofen count doughnuts and eggs by dozens. Similarly, we count shoes and gloves in pairs. Chemists, however, do not work with macroscopic (visible) objects like shoes and doughnuts. Instead, chemists are interested in microscopic entities: atoms and molecules. Since these entities are so small, chemists established their own practical counting unit called the mole. So we can say that A Mole is a Chemist Dozen.

    Answered by Naveen Sharma (Feb 22, 2017 12:07 p.m.)
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A bag filled with air has volume of 500 cubic cm. Calculate force required to immerse it completely in water. 

Posted by Aryan Malewar (Feb 22, 2017 7:15 a.m.) (Question ID: 2426)

What is freefall

Posted by spandan Mukhopadhyay (Feb 22, 2017 12:07 a.m.) (Question ID: 2425)

  • Answers:
  • It is the condition of unrestrained motion in a gravitational field. For e.g.: Parachute Jump before the parachute opens.

    Answered by Manish Gandhi (Feb 22, 2017 12:30 p.m.)
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Why  can't  the number of protons be more than number of neutrons in an atom?

Posted by Pranzal Kumar Sinha (Feb 21, 2017 8:35 p.m.) (Question ID: 2410)

  • Answers:
  • The reason is that protons, being charged particles, repel each other. As you get to heavier elements, with each new proton you add, there is a larger repulsive force. The nuclear force is attractive and stronger than the electrostatic force, but it has a finite range. So you need to add extra neutrons, which do not repel each other, to add extra attractive force. 

    Answered by Shweta Gulati (Feb 21, 2017 9:12 p.m.)
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a man fires a bullet towards cliff and hears echo after 4 sec he moves towards the clife nabout 150m and agains fire now he hears echo after3.6s what is the distance from his first position[ASSUME VELOCITY OF SOUND IS NOT KNOWN TO YOU]

Posted by Yuvraj Singh (Feb 21, 2017 5:31 p.m.) (Question ID: 2400)

  • Answers:
  • Ans. Let the Distance  b/w cliff and man = d m

    Then total distance cover by sound = 2d m

    Velocity of Sound = v 


    \(v = {2d \over 4} = {d\over 2}\space\space\space\space\space\space\space\space\space\space ......[1]\)

    As He move 150m  towards The cliff, 

    Now distance b/w man and cliff = d-150 m

    Total distance covered by Sound = 2(d-150) m


    \(v = {2(d-150)\over 3.6} = {2(d-150)\times 10\over 36} = {5(d-150)\over 9} \space \space \space \space \space ......[2]\)

    As velocity of sound is same, then 

    from (1) and (2)

    => \({d\over 2}= {5(d-150)\over 9} \)

    => \(9d = 10d - 1500 \)

    => \(10d- 9d = 1500 => d = 1500 \)

    Distance b/w man and cliff = 1500 m

    Answered by Naveen Sharma (Feb 21, 2017 5:49 p.m.)
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Write the character sketch of jerome on the basis of the chapter 11 to 19 in "Three Men in a Boat "

Posted by khan subhajit (Feb 21, 2017 9:35 a.m.) (Question ID: 2389)

  • Answers:
  • Providing some points, Write them in your own words.

    • The narrator, a happy-go-lucky young man like his two friends
    • Fond of animals, as seen in his interactions with cats and his dog, Montmorency.
    • Hypochondriac, imagining that he had all the imaginable diseases of the world, just by reading about them.
    • More sensible and practical than the other two and shows a knowledge and appreciation for the historical aspect of the English countryside.
    • Like his friends, he too disliked hard work, and was convinced that he had been labouring the most while the other two lazed about.
    • More romantic and imaginative soul, with his head often in the clouds, as he lost sight of the fact that he was steering time and again, while admiring the scenery. He was the most affected by the beauties of nature. In fact, he had turned down the inn at Datchet initially because it did not have honeysuckle growing over it and hence was not picturesque enough.
    • Keenest sense of aesthetics as he constantly critiques his friends choices of clothing.
    • sense of humour and maintained a steady balance between the diverse personalities of George and Harris .
    Answered by Naveen Sharma (Feb 21, 2017 10:34 a.m.)
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Does gujjar herders of eastern side and gujjar bakarwals are same?

Posted by Ishita Khurana (Feb 21, 2017 9:19 a.m.) (Question ID: 2388)

If x+ y = 21 and x × y= 80 then find x and y.

Posted by SHRI NIWAS JAT (Feb 21, 2017 7:33 a.m.) (Question ID: 2382)

  • Answers:
  • Ans. x + y = 21 ......(1)

    xy = 80   .....(2)

    From (1)

    x = 21-y

    (21-y)×y = 80

    => 21y - y2 = 80

    => y-21y +80 = 0

    => y2 -16y -5y +80=0

    => y(y-16)-5(y-16) = 0

    => (y-16)(y-5) = 0

    => y = 16 or y = 5

    If y =16 then x = 5

    If y =5 then x =16

    Answered by Naveen Sharma (Feb 21, 2017 8:34 a.m.)
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State some of the uses of Gymnosperms with its source.

Posted by JD Shukla (Feb 20, 2017 9:06 p.m.) (Question ID: 2372)

  • Answers:
  • Ans. Some plants seeds are edible, rich in starch and stems and leaves are used for making wine while leaves, pollen, bark and oil of some species are an effective ingredient in medicines. The ornamental trees are utilized in landscaping and parks. In industry, pulp and wood from the plants produce everything from pencils to turpentine. Conifers, such as pine and cedar, provide lumber and some species are used for nail polish, soap and perfume.

    Answered by Naveen Sharma (Feb 20, 2017 9:40 p.m.)
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Name the products obtained from some of the pteridophyta also tell the source.


Posted by JD Shukla (Feb 20, 2017 9:05 p.m.) (Question ID: 2371)

  • Answers:
    • Some examples are marsilea, ferns and horse-tails.
    • Pteridophytes are used for medicinal purposes and as soil-binders. They are also frequently grown as ornamentals.
    Answered by Shweta Gulati (Feb 21, 2017 7:32 p.m.)
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How can we use algae ? Please explain in detail.

Posted by JD Shukla (Feb 20, 2017 9:03 p.m.) (Question ID: 2370)

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  • Humans use algae as food, for production of useful compounds, as biofilters to remove nutrients and other pollutants from wastewaters, to assess water quality, as indicators of environmental change, in space technology, and as laboratory research systems. Algae is commercially cultivated for Pharmaceuticals, Nutraceuticals, Cosmetics and Aquaculture purpose.

    Answered by Shweta Gulati (Feb 21, 2017 7:35 p.m.)
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A Cube of side 4cm contains a sphere touching its sides.Find the voloume of the gap in between.


Posted by Rahul Maheshwari (Feb 20, 2017 2:32 p.m.) (Question ID: 2361)

  • Answers:
  • Ans. Side of Cube (a) = 4 cm

    Volume of Cube = \(a^3 = 4 \times 4 \times 4 = 64 cm^3\)

    As the Sphere touch the side of Cube

    So, Diameter of Sphere = 4 cm

    Radius of Sphere(r) = 4/2 = 2 cm

    Volume of Sphere = \({4\over 3} \times \pi \times r^3 = {4\over 3} \times {22\over 7}\ \times 8 = {704\over 21} = 33.5 cm^3\)

    Volume of Gap = Volume of Cube - Volume of Sphere 

    => 64 - 33.5 = 30.5cm3

    Answered by Naveen Sharma (Feb 20, 2017 2:52 p.m.)
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How to find cube root? 

Posted by happy thawani (Feb 20, 2017 2:15 p.m.) (Question ID: 2360)

  • Answers:
  • there is two process finding the cube root

    1. prime factorisation

    2. estimatiosation 

    for estimation

    A. divide the nuber into two group, from right most choose only three number,remaining number should other group

    for example 17576,,group1=17 and group=576

    B. look the group2 last number is its one digit of cuberoot should 6

    C. 17 lie between 23 and 33,for the estimation we choose smallest number i.e 2

    thus cuberoot of 17576 is 26 

    similarly, cube root of 85375 is 95

    sorry for text problem in previous answer

    Answered by imran khan (Feb 22, 2017 12:40 p.m.)
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find the number of electron ,proton,&neutron possessed by the alpha particles(4/2He+++)used in the gold leaf experiment.

Posted by Ankit Jhinjhonkar (Feb 20, 2017 9:25 a.m.) (Question ID: 2352)

  • Answers:
  • Ans.

    Number of Electron = 0

    Number of Proton = 2

    Number of Neutron = 2

    Answered by Naveen Sharma (Feb 20, 2017 12:14 p.m.)
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  1. In a frequency distribution, the class mark of a class is 10 and width is 8 .find lowest limit.?..fst..plss..
Posted by Bhavik Kalal (Feb 20, 2017 1:44 a.m.) (Question ID: 2347)

  • Answers:
  • Let a and b represent the lower and upper limits of a class interval respectively

    Class mark = 10 

    Class size = 8

    Lower limit = Class mark - Half of class size

    = 10 -4 = 6

    Upper limit = Class mark + Half of class size

    = 10+4 = 14 

    Answered by Shweta Gulati (Feb 20, 2017 2:23 a.m.)
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Why all the isotopes are not placed in periodic table?

Posted by SUMANA ROY (Feb 19, 2017 10:17 p.m.) (Question ID: 2345)

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  • Since all the isotopes of an element have the same atomic  number,they can be put at one place in the same group of the periodic table. For example,both the isotopes of chlorine, Cl-35 and Cl-37 ,have the same atomic number of 17,so both of them can be put at one place in the same group of the periodic table.

    Answered by Shweta Gulati (Feb 20, 2017 12:38 a.m.)
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Weight of an empty glass is 1N. When it is completely filled with water the weight observed is 4N. If you throw the water and fill the empty glass partly with sand and its weight becomes 4N, if the rest of glass is now filled up with water, the weight becomes 6N, what is relative density of sand?

Posted by Harsh Jain (Feb 19, 2017 9:35 p.m.) (Question ID: 2344)

  • Answers:
  • Weight of empty glass = 1N

    Weight of water alone = 4N-1N= 3N

    Weight = mg

    Mass of water = 3/9.8 = 0.306 kg

    Density of water = 1000kg/m3

    Volume of glass = 0.306/1000 = 3.06 X 10-4 m3

    Weight of half glass sand = 4N-1N =3N

    Weight of full glass sand = 3N+3N = 6N

    Mass of full glass sand= 6N/9.8 = 0.612kg

    Density of sand = Mass of sand/Volume of glass = 0.612/(3.06 X 10-4= 2000kg/m3

    Relative density of sand = Density of sand/Density of water

    = 2000/1000 =2


    Answered by Shweta Gulati (Feb 20, 2017 12:52 a.m.)
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Posted by Jagruti Kar (Feb 19, 2017 7:44 p.m.) (Question ID: 2339)

  • Plz ans fast!!

    Posted by Jagruti Kar (Feb 19, 2017 8:04 p.m.)
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if the distance  of the chord from the radius is 5cm and the length of the chord is 4cm find the radius of the circle


Posted by syed mir (Feb 19, 2017 7:04 p.m.) (Question ID: 2338)

  • Answers:
  • Let AB be the chord of length 4 cm. C be its mid-point

    . O be the center of the circle. Join OA [OA becomes the radius]

    Given OC = 5 cm

    AC = BC = 4/2 = 2 cm [The perpendicular drawn from the center to a chord bisect the chord]

    OAC is a right angled triangle


    OA2= 52+22

    = 25+4


    OA= \(\sqrt29\)cm

    You can refer this image. Just make a few changes according to the question.

    Answered by Shweta Gulati (Feb 20, 2017 1:04 a.m.)
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Who wrote the cricket laws ?

Posted by D.Abishai Christopher Singh (Feb 19, 2017 1:38 p.m.) (Question ID: 2330)

  • You can see in the book its written their.

    Posted by Uditkumar Swami (Feb 19, 2017 6:05 p.m.)
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  • Answers:
  • Ans.Marylebone Cricket Club (MCC) has been the owner of the Laws of Cricket since the 18th century.

    Answered by Naveen Sharma (Feb 19, 2017 8:25 p.m.)
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What is the need for political institutions?

Posted by Happy Gill (Feb 19, 2017 1:05 p.m.) (Question ID: 2328)

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  • If there is no political institution then they will be no functioning of government and there is no making of laws.

    Answered by D.Abishai Christopher Singh (Feb 19, 2017 1:40 p.m.)
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The velocity of an object is suddenly doubled.if its kinetic energy earlier was 100 j what is the new kinetic  energy?

Posted by AARTI SHARMA (Feb 19, 2017 11:59 a.m.) (Question ID: 2326)

  • Answers:
  • Kinetic energy = 1/2 mv2 

    If velocity is doubled then KE increases  4 times.

    So the answer would be 4*100= 400 joules

    Answered by ayush das (Feb 19, 2017 12:13 p.m.)
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A sound produced have 20 rarefaction and compressions in 0.2 sec . Distance between compression and rarefaction is 50cm find wavelength ,frequency,and time period of wave.

Posted by SHRI NIWAS JAT (Feb 19, 2017 10:02 a.m.) (Question ID: 2324)

  • Answers:
  • Since time perios is the time taken to complere one rarefaction and one compression:-

    Now, time taken to complete 20 compressions and rarefactions:- 0.2 sec:-

    time taken to complere one rarefaction and one compression = 0.2/20

    = 0.01sec = time period

    Since f=1/t

    Therefore f= 1/0.01 = 100 hz

    and labda = 2*50=100cm


    Answered by Devanshu Agarwal (Feb 19, 2017 11:03 a.m.)
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A sound wave has frequency of 2 kHz and wavelength 40 cm . Calculate time taken in 1.6 km


Posted by SHRI NIWAS JAT (Feb 19, 2017 9:59 a.m.) (Question ID: 2323)

  • Answers:
  • Since s=wavelength * frequency ( s= speed of sound)

    Therefore :- s  = (40/100) * 2000

     = 800 m/s

    Therefore time taken = (1600)/800

    = 2 sec

    Answered by Devanshu Agarwal (Feb 19, 2017 10:43 a.m.)
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What is formula of finding time period in  chapter sound

Posted by SHRI NIWAS JAT (Feb 19, 2017 9:57 a.m.) (Question ID: 2321)

  • Answers:
  • Since time period(T) is the time taken to complete one cycle

    and frequency(f) is the no. of cycles completed in 1 sec:-

    THerefore T = 1/f.


    Answered by Devanshu Agarwal (Feb 19, 2017 10:48 a.m.)
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What is natural resources


Posted by Arpan Mandal (Feb 18, 2017 10:27 p.m.) (Question ID: 2309)

  • Answers:
  • the substances obtained from natural sources like sun,  plant (renewable or non renewable) are called natural sources.

    Answered by Supriya Kumari (Feb 18, 2017 11:49 p.m.)
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Please give some exceptional organisms of each kingdom with its exceptional characteristics

Posted by JD Shukla (Feb 18, 2017 10:11 p.m.) (Question ID: 2306)

please some of the exceptional spieces for each kingdom with its exceptional characteristics.

Posted by JD Shukla (Feb 18, 2017 10:09 p.m.) (Question ID: 2305)

  • please answer fast!.!


    Posted by JD Shukla (Feb 20, 2017 8:50 p.m.)
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In which year was indian forest service setup ? 

Posted by Krishna Singh (Feb 18, 2017 9:14 p.m.) (Question ID: 2303)

  • Answers:
  • It was set up in 1965 under all india forest act.

    Answered by Vishu Tomar (Feb 19, 2017 10:06 a.m.)
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  • Ans. Indian Forest Service was created in 1966 under the All India Services Act 1951.

    Previously, the Imperial Forestry Service existed during the British Raj from 1865 to 1935. 

    Officers are recruited via a rigorous competitive examination and then trained for about two years by the Central Government.

    Answered by Naveen Sharma (Feb 18, 2017 10:13 p.m.)
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what were the sumptury law in France ? 

Posted by Krishna Singh (Feb 18, 2017 9:10 p.m.) (Question ID: 2302)

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