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Tue September 23, 2014  

Ans: The colour of our hair depends on the concentration of melanin pigment. Melanin is of two types: eumelanin and pheomelanin. Generally, if more eumelanin is present, the colour of the hair is darker. If less eumelanin is present, the hair is lighter. Levels of melanin can vary over time causing a person's hair colour to change.

Tue September 23, 2014  

Ans: At normal  temperature, the surface of copper is covered with copper oxide. The thin layer of copper oxide is a protective cover which protects copper from further oxidation. Thus this copper oxide does not burn as it  is already reacted with the oxygen in the air. No further oxidation can occur.

Tue September 23, 2014  

Ans: Burning of any substance depends upon its ignition temperature. Iron fillings are small in size as compare to iron due to which they can achieve their ignition temperature easily. So iron fillings burn vigorously when sprinkled in a burner but not Iron.

Tue September 23, 2014  

Ans: Movements in plants are of two types: Nastic movements and Tropic movements. Nastic movements: The movement of a plant in response to an external stimulus in which the direction of response is not determined by the direction of stimulus is called nastic movement. Examples: 1. Daisy flowers close at dusk and open at daybreak. 2. Mimosa pudica or the touch-me-not plant has tiny leaflets which fold up in response to mechanical stimuli such as touch, drops of rain or even a gust of wind. Nastic movements can be of two types: photonasty and nyctinasty. Photonasty is a nastic movement to the light and dark phases of the day. Example: Flowers of primrose blossom during the evening but close during the day. Nyctinasty is the movement in response to dark. Example: Leaves of the rain tree fold by nightfall. Tropic movements: The movement of plant organs towards or away from a stimulus is known as tropism or tropic movement. The stimulus can be some agent or action which evokes a movement in the plant. Tropic movements can be of the following types: 1. Phototropism : The movement of plant parts towards or away from light is termed as phototropism. Example: Roots grow away from the light. 2. Geotropism : The movement of plant organs in response to gravity is termed as geotropism. Example: The shoot grows upwards against gravity. 3. Chemotropism : The movement of plant organs in response to a chemical stimulus is called chemotropism. Example: The pollen tube grows towards the sugary substance secreted by the stigma of the flower. 4. Hydrotropism : The movement of plant organs in response to water is termed hydrotropism. Example: Roots grow towards the source of moisture. 5. Thigmotropism : The movement of plant organs in response to stimuli caused by physical contact with solid objects is termed thigmotropism. Example: Weak-stemmed plants use twining stems and tendrils to climb on other plants/objects which provide them support. 

Mon September 22, 2014  

Ans: Some pesticides do not break down for a long time. They retain their chemical effects in soil, water, wildlife, air and humans as a side effect of their use on pests. Such pesticides are called non-biodegradable pesticides. Example: D.D.T and Dieldrin can still be found in the environment today, although they are no longer available and have not been used for many years. 

Mon September 22, 2014  

Ans: (i) The solution for this subquestion can be done using Fibonacci sequence which is not in your syllabus.   (ii)    

Mon September 22, 2014  

Ans: T h e space a b o v e space s u m space i s space t o space b e space s o l v e d space b y space u sin g space sin e space r u l e L e t space angle B equals x comma space angle A equals 2 x comma space angle C equals 180 degree minus 3 x fraction numerator a over denominator sin space A end fraction equals fraction numerator b over denominator sin space B end fraction equals fraction numerator c over denominator sin space C end fraction o r comma space fraction numerator a over denominator sin space 2 x end fraction equals fraction numerator b over denominator sin space x end fraction equals fraction numerator c over denominator sin left parenthesis 180 minus 3 x right parenthesis end fraction o r comma fraction numerator a over denominator 2 sin space x. cos space x end fraction equals fraction numerator b over denominator sin space x end fraction equals fraction numerator c over denominator sin space 3 x end fraction o r comma fraction numerator a over denominator 2 sin space x. cos space x end fraction equals fraction numerator b over denominator sin space x end fraction equals fraction numerator c over denominator 3 sin space x minus 4 sin cubed x end fraction o r comma fraction numerator a over denominator 2 cos space x end fraction equals b equals fraction numerator c over denominator 3 minus 4 sin squared x end fraction space left square bracket M u l t i p l y i n g space b y space sin space x space o n space a l l space t h e space t h r e e space t e r m s right square bracket space l e t space fraction numerator a over denominator 2 cos space x end fraction equals b o r comma space cos space x equals fraction numerator a over denominator 2 b end fraction............. left parenthesis i right parenthesis l e t space b equals fraction numerator c over denominator 3 minus 4 sin squared x end fraction o r comma space 3 minus 4 sin squared x equals c over b o r comma space 3 minus 4 left parenthesis 1 minus cos squared x right parenthesis equals c over b o r comma space 3 minus 4 plus 4 space cos squared x equals c over b o r comma space 4 space cos squared x equals c over b plus 1 o r comma space cos squared x equals fraction numerator c plus b over denominator 4 b end fraction S u b s t i t u t i n g space cos space x space i n space t h e space a b o v e space e q u a t i o n comma o r comma space fraction numerator a squared over denominator 4 b squared end fraction equals fraction numerator c plus b over denominator 4 b end fraction o r comma space a squared over b equals c plus b space space space space space space space left square bracket space because b not equal to 0 right square bracket o r comma space a squared equals b left parenthesis b plus c right parenthesis

Mon September 22, 2014  

Ans: Error: the service is unavailable.

Mon September 22, 2014  

Ans: n to the power of 6 plus 3 n to the power of 5 minus 5 n to the power of 4 minus 15 n cubed plus 4 n squared plus 12 n plus 3 equals n to the power of 5 left parenthesis n plus 3 right parenthesis minus 5 n cubed left parenthesis n plus 3 right parenthesis plus 4 n left parenthesis n plus 3 right parenthesis plus 3 equals left parenthesis n plus 3 right parenthesis left parenthesis n to the power of 5 minus 5 n cubed plus 4 n right parenthesis plus 3 equals left parenthesis n plus 3 right parenthesis n left parenthesis n to the power of 4 minus 5 n squared plus 4 right parenthesis plus 3 equals left parenthesis n plus 3 right parenthesis n left parenthesis n to the power of 4 minus 4 n squared minus n squared plus 4 right parenthesis plus 3 space space space left square bracket F a c t o r i z i n g right square bracket equals left parenthesis n plus 3 right parenthesis n left parenthesis n squared left parenthesis n squared minus 4 right parenthesis minus 1 left parenthesis n squared minus 4 right parenthesis right parenthesis plus 3 equals left parenthesis n plus 3 right parenthesis n left parenthesis n squared minus 1 right parenthesis left parenthesis n squared minus 4 right parenthesis plus 3 equals left parenthesis n plus 3 right parenthesis n left parenthesis n plus 1 right parenthesis left parenthesis n minus 1 right parenthesis left parenthesis n plus 2 right parenthesis left parenthesis n minus 2 right parenthesis plus 3 equals left parenthesis n minus 2 right parenthesis left parenthesis n minus 1 right parenthesis n left parenthesis n plus 1 right parenthesis left parenthesis n plus 2 right parenthesis left parenthesis n plus 3 right parenthesis plus 3 S i n c e space t h e space a b o v e space f o r m space c a n n o t space b e space w r i t t e n space f o r space a n y space f o r m space o f space a space p e r f e c t space s q u a r e comma space t h e r e f o r e space i t space i s space n o t space a space p e r f e c t space s q u a r e.

Mon September 22, 2014  

Ans: C o n s i d e r space t h e space g i v e n space p o l y n o m i a l comma f open parentheses x close parentheses equals 2 x cubed minus x squared minus 4 x plus 3 f open parentheses 1 close parentheses equals 2 open parentheses 1 close parentheses cubed minus 1 squared minus 4 open parentheses 1 close parentheses plus 3 equals 2 minus 1 minus 4 plus 3 equals 0 B y space t r i a l space a n d space e r r o r space m e t h o d comma space 1 space i s space t h e space r o o t space o f space t h e space a b o v e space e q u a t i o n. T h u s comma space d i v i d e space 2 x cubed minus x squared minus 4 x plus 3 space b y space x minus 1 space t o space g e t space 2 x squared plus x minus 3 A g a i n space f a c t o r i n g space 2 x squared plus x minus 3 : 2 x squared plus x minus 3 equals 2 x squared minus 2 x plus 3 x minus 3 equals 2 x open parentheses x minus 1 close parentheses plus 3 open parentheses x minus 1 close parentheses equals open parentheses 2 x plus 3 close parentheses open parentheses x minus 1 close parentheses T h u s comma space 2 x cubed minus x squared minus 4 x plus 3 equals open parentheses 2 x plus 3 close parentheses open parentheses x minus 1 close parentheses open parentheses x minus 1 close parentheses

Mon September 22, 2014  

Ans: Dear patratitas@gmail.com

Thanks for asking us a question in Ask the Expert section of TopperLearning.com.
The scope of this helpdesk is to answer subject related queries which are relevant to understanding concepts and solving problems. Hence we regret that we would not be able to answer your query.

Regards

Topperlearning Team.

Mon September 22, 2014  

Ans: Dear baruahn2012@gmail.com

Thanks for asking us a question in Ask the Expert section of TopperLearning.com.
Sulphur has big size. Repulsion between the lone pairs on sulphur is less in S – S bond due to which bond dissociation energy is high. Sulphur has vacant orbital which can be extended to higher valency. Due to this sulphur shows strong catenation tendency. Sulphur shows catenation upto 8 atoms in the formation of S 8 molecule of sulphur. H 2 S 2 , H 2 S 3 , H 2 S 4 are the other examples of sulphur catenation.

Regards

Topperlearning Team.

Mon September 22, 2014  

Ans:

Mon September 22, 2014  

Ans:

Mon September 22, 2014  

Ans:

Mon September 22, 2014  

Ans: Retardation means negative acceleration . The velocity of a body may increase or decrease .Acceleration takes place when the velocity of a body changes. So when the velocity of a body increase, the acceleration is said to be positive and when the velocity of a body decrease, the acceleration is said to be negative(Retardation) .A body is said to be retarded if its velocity is decreasing.  Eg: a train is said to be retarded when it slows down on reaching a station,i.e. the velocity decreases.Retardation is acceleration with negative sign. Or negative value of acceleration shows that the velocity of a body is decreasing.

Mon September 22, 2014  

The mean of the following frequency distribution is 145.Find the missing freguencies x and y.
 
                   CLASS                                         FREQUENCY
                    0-50                                               6
                    50-100                                           X
                   100-150                                          64
                   150-200                                          52
                   200-250                                           Y
                   250- 300                                         14
                   TOTAL                                             200
Ans: Class Frequency x i u subscript i equals fraction numerator x subscript i space minus a over denominator h end fraction space space space space equals space fraction numerator x subscript i space minus space 175 over denominator 50 end fraction f i u i 0 - 50 6 25 -3 -18 50 - 100 x 75 -2 -2x 100 - 150 64 125 -1 -64 150 - 200 52 175 0 0 200 - 250 y 225 1 y 250 - 300 14 275 2 28   sum for blank offi = 200     Syntax error from line 1 column 49 to line 1 column 73. Unexpected ' Access Denied     	Sorry, You don't have permission to view that page. 	 = -54 - 2x + y
                               Let the assumed mean a = 175, h = 50   Also sum for blank offi = 200 = 136 + x + y 54 = x + y .....(1) Syntax error from line 1 column 49 to line 1 column 73. Unexpected ' Access Denied     	Sorry, You don't have permission to view that page.

Mon September 22, 2014  

In a hospital,during the month of October 3013,number of patients admitted for dengue and their ages are as follows:
 
             AGE (IN YEARS)                                                    NUMBER  OF
                                                                                         PATIENTS  
               0-8                                                                       10
               8-16                                                                     12
               16-24                                                                    8
               24-32                                                                   25
               32-40                                                                   15
               40-48                                                                   11
               48-56                                                                   21
               56-64                                                                   30
               64-72                                                                   22
 
                   Find the mean and median age of the patients.
Ans: Here class length h = 8, Assumed mean = 4 Class Frequency Midvalues xi ui = (xi - a)/h fiui c.f. 0 - 8 10 8 -5 -50 10 8 - 16 12 12 -4 -48 22 16 - 24 8 20 -3 -24 30 24 - 32 25 28 -2 -50 55 32 - 40 15 36 -1 -15 70 40 - 48 11 44 0 0 81 48 - 56 21 52 1 21 102 56 - 64 30 60 2 60 132 64 - 72 22 68 3 66
154 Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '. Now for median, N = 154, then N/2 = 77, the median class will be 40-48, then l = 40, f = 11, C = 70 Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.

Mon September 22, 2014  

Ans: How I Taught My Grandmother to Read is a short story written by Sudha Murthy who remembers one of her childhood experiences when her grandmother wanted to learn alphabets.The author was still young and the story is about a time when there was no television serials or movies in India.  Elders took  interest in stories and novels published in a popular Kannada magazine. One of the novels was Kaashi Yatre, written by Triveni. It was a favorite novel for Sudha Murthy’s grandmother too, as the grandmother identified her with this old woman in the novel. Like the old woman in the novel, the grandmother also had dreams in life – dream to get educated. However, after being married at a young age and bearing children, the grandmother had to abandon studies. Grandmother would ask Sudha to read the novel to her. Once, when Sudha  had gone for a wedding, the grandmother could not find anyone who could read her the novel. When Sudha returned from the wedding, grandmother was in tears. She woke Sudha up in  the middle of a night and requested her to start her classes. Grandmother explained her little granddaughter about her long forgotten love to learn reading and writing. Sudha agreed to teach her grandmother. In a few days grandmother learnt alphabets. On the day of Durga Puja, she read the title of the book, Kaashi Yatre. Sudha gave her a copy of the book Kaashi Yatre and grandmother touched her feet in respect; as a student touching the feet of a teacher.

Mon September 22, 2014  

Ans: According to the right hand thumb rule: If you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of the current. Then, your fingers will wrap around the conductor in the direction of the field lines of the magnetic field. In this case, consider that a circular loop of wire is lying on the plane of the table as shown. Let the current pass through the loop in the clockwise direction. On applying the right hand thumb rule to the right side and left side of the loop:  For the right side of the circular loop: The direction of magnetic field lines will be as if they are emerging from the table outside the loop and while they will be going into the table inside the loop as shown in the figure. Similarly for the left side of the circular loop: The direction of magnetic field lines inside the loop will also be going into the table while outside the loop they will be emerging from the table as shown.
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