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

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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.
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A bag filled with air has volume of 500 cubic cm. Calculate force required to immerse it completely in water.

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What is freefall

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It is the condition of unrestrained motion in a gravitational field. For e.g.: Parachute Jump before the parachute opens.
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Why can't the number of protons be more than number of neutrons in an atom?

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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.
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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]

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Ans. Let the Distance b/w cliff and man = d m
Then total distance cover by sound = 2d m
Velocity of Sound = v
Then
\(v = {2d \over 4} = {d\over 2}\space\space\space\space\space\space\space\space\space\space ......[1]\)
As He move 150m towards The cliff,
Now distance b/w man and cliff = d150 m
Total distance covered by Sound = 2(d150) m
So
\(v = {2(d150)\over 3.6} = {2(d150)\times 10\over 36} = {5(d150)\over 9} \space \space \space \space \space ......[2]\)
As velocity of sound is same, then
from (1) and (2)
=> \({d\over 2}= {5(d150)\over 9} \)
=> \(9d = 10d  1500 \)
=> \(10d 9d = 1500 => d = 1500 \)
Distance b/w man and cliff = 1500 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 "

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Providing some points, Write them in your own words.
 The narrator, a happygolucky 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 .
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Does gujjar herders of eastern side and gujjar bakarwals are same?

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

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Ans. x + y = 21 ......(1)
xy = 80 .....(2)
From (1)
x = 21y
(21y)×y = 80
=> 21y  y^{2} = 80
=> y^{2 }21y +80 = 0
=> y^{2} 16y 5y +80=0
=> y(y16)5(y16) = 0
=> (y16)(y5) = 0
=> y = 16 or y = 5
If y =16 then x = 5
If y =5 then x =16
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State some of the uses of Gymnosperms with its source.

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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.
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Name the products obtained from some of the pteridophyta also tell the source.

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 Some examples are marsilea, ferns and horsetails.
 Pteridophytes are used for medicinal purposes and as soilbinders. They are also frequently grown as ornamentals.
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How can we use algae ? Please explain in detail.

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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.
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A Cube of side 4cm contains a sphere touching its sides.Find the voloume of the gap in between.

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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 = 30.5cm^{3}
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How to find cube root?

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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 6.so its one digit of cuberoot should 6
C. 17 lie between 2^{3} and 3^{3},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
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find the number of electron ,proton,&neutron possessed by the alpha particles(4/2He+++)used in the gold leaf experiment.

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Ans.
Number of Electron = 0
Number of Proton = 2
Number of Neutron = 2
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 In a frequency distribution, the class mark of a class is 10 and width is 8 .find lowest limit.?..fst..plss..

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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
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Why all the isotopes are not placed in periodic table?

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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, Cl35 and Cl37 ,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.
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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?

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Weight of empty glass = 1N
Weight of water alone = 4N1N= 3N
Weight = mg
Mass of water = 3/9.8 = 0.306 kg
Density of water = 1000kg/m^{3}
Volume of glass = 0.306/1000 = 3.06 X 10^{4} m^{3}
Weight of half glass sand = 4N1N =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/m^{3}
Relative density of sand = Density of sand/Density of water
= 2000/1000 =2
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ABCD is a parallelogram and E AND F ARE THE MID POINTS OF THE SIDES DC AND AB RESPECTIVELY . SHOW THAT ar(AEF) =ar(CFE)

Plz ans fast!!
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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

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Let AB be the chord of length 4 cm. C be its midpoint
. 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
OA^{2}=OC^{2}+AC^{2}[byPythagorasTheorem]
OA^{2}= 5^{2}+2^{2}
= 25+4
=29
OA= \(\sqrt29\)cm
You can refer this image. Just make a few changes according to the question.
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Who wrote the cricket laws ?

You can see in the book its written their.
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Ans.Marylebone Cricket Club (MCC) has been the owner of the Laws of Cricket since the 18th century.
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What is the need for political institutions?

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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.
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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?

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Kinetic energy = 1/2 mv^{2}
If velocity is doubled then KE increases 4 times.
So the answer would be 4*100= 400 joules
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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.

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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
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A sound wave has frequency of 2 kHz and wavelength 40 cm . Calculate time taken in 1.6 km

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Since s=wavelength * frequency ( s= speed of sound)
Therefore : s = (40/100) * 2000
= 800 m/s
Therefore time taken = (1600)/800
= 2 sec
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What is formula of finding time period in chapter sound

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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.
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What is natural resources

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the substances obtained from natural sources like sun, plant (renewable or non renewable) are called natural sources.
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Please give some exceptional organisms of each kingdom with its exceptional characteristics

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

please answer fast!.!
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In which year was indian forest service setup ?

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It was set up in 1965 under all india forest act.
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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.
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what were the sumptury law in France ?

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