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Thu August 21, 2014  

Ans: Fleming’s left-hand rule gives the direction of magnetic force acting on a conductor whereas Fleming’s right-hand rule is used to find the direction of induced current.Fleming's left-hand rule is used to find the direction of magnetic force acting in an  electric motors while Fleming's right-hand rule is used to find the direction of induced current in an  electric generators. An electric current and magnet field exist in an electric motor, and they lead to the force that creates the motion , and so the left hand rule is used which gives the direction of magnetic force acting. In an electric generator, the motion (due to force) and magnetic field exist and they lead to the production of an electric current , and so the right hand rule is used which helps us to find the direction of induced current. Fleming’s right-hand rule : According to this rule, “Stretch the thumb, forefinger and middle finger of the right hand such that they are mutually perpendicular to each other. If the forefinger points indicates the direction of the magnetic field and the thumb indicates the direction of motion of the conductor, then the middle finger will indicate the direction of induced current in the conductor”.
Fleming’s left-hand rule : According to this rule, “Stretch the thumb, forefinger and middle finger of the left hand such that they are mutually perpendicular to each other. If the forefinger points in the direction of magnetic field and the middle finger indicates the direction of the current, then the thumb will indicate the direction of motion or the force on the conductor”.

Thu August 21, 2014  

Ans: fraction numerator 1 over denominator square root of 3 plus square root of 5 minus square root of 7 end fraction  R a t i o n a l i s e space d e n o m i n a t o r comma space w e space g e t  fraction numerator 1 over denominator open parentheses square root of 3 plus square root of 5 close parentheses minus open parentheses square root of 7 close parentheses end fraction cross times fraction numerator open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses over denominator open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses end fraction  equals fraction numerator open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses over denominator open parentheses square root of 3 plus square root of 5 close parentheses squared minus open parentheses square root of 7 close parentheses squared end fraction  equals fraction numerator open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses over denominator 3 plus 5 plus 2 square root of 15 minus 7 end fraction  equals fraction numerator open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses over denominator 1 plus 2 square root of 15 end fraction  R a t i o n a l i s e space d e n o m i n a t o r space a g a i n equals fraction numerator open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses over denominator 1 plus 2 square root of 15 end fraction cross times fraction numerator 2 square root of 15 minus 1 over denominator 2 square root of 15 minus 1 end fraction  equals fraction numerator open square brackets open parentheses square root of 3 plus square root of 5 close parentheses plus open parentheses square root of 7 close parentheses close square brackets cross times open square brackets 2 square root of 15 minus 1 close square brackets over denominator 59 end fraction  equals 1 over 59 open square brackets 6 square root of 5 minus square root of 3 plus 10 square root of 3 minus square root of 5 plus 2 square root of 135 minus square root of 7 close square brackets  equals 1 over 59 open square brackets 5 square root of 5 plus 9 square root of 3 plus 2 square root of 135 minus square root of 7 close square brackets

Thu August 21, 2014  

Ans: According to the second law of motion we know that moving bodies possess momentum and is equal to the product of mass and velocity.                                      p = m v According to the law of conservation of momentum " When two or more bodies act upon one another, their total momentum remains constant provided no external force are acting." Consider a collision between a moving and a stationary object. When the collision occurs, the velocity of the moving object decreases, but at the same time, the velocity of the stationary object increases.Due to this the momentum of moving object decreses and the momentum of the stationary object increases.The increase in the momentum of the stationary object is equal to the decrease in the momentum of the moving object.Thus there is no loss of momentum during collision. Thus, the law of conservation of momentum can be stated as the sum of momenta of objects before collision is equal to the sum of momenta after collision, provided there is no external force acting on the objects.   Consider two objects A and B of masses m A and m B initially moving in a straight line with velocities u A and u B , respectively. Assume that u A > u B . They collide with each other as shown below. The total momentum of the two objects before collision is m A u A +m B u B .      The collision lasts for time t . During this collision, A exerts a force F AB on B and B exerts a force F BA on A.Suppose v A and v B are the velocities of A and B after collision, the momentum before and after collision for object A is m A u A and m A v A  respectively. Thus, according to Newton's law, the force F AB   can be written as :                               Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.
  Similarly , the force F BA  on A is:                              Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '. According to the third law of motion, we have : Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.
 i.e The total momentum of both objects A and B before collision is equal to the total momentum of both objects after collision. Thus, the momentum is conserved in a collision.

Thu August 21, 2014  

Ans: MITOSIS: Mitosis consists of the following phases: Karyokinesis : It is the division of the nucleus during cell division. Cytokinesis : It is the division of the cytoplasm during cell division. Karyokinesis occurs in four phases: Prophase: chromatin fibres condense and thick chromosomes are visible. Sister chromatids are attached to each other at the centromere . Centrioles duplicate and formation of spindle apparatus begins. The nucleolus and nuclear membrane disappear. Metaphase:  Chromosomes are arranged on the metaphase plate or equatorial plane. Anaphase: The centromere divides and the sister chromatids separate from each other. Spindle fibres contract and pull chromatids towards opposite poles. Telophase: Spindle fibres disappear. Chromosomes become thin and turn into chromatin fibres. Nuclear membranes appear around each set of daughter chromosomes at two opposite poles. Nucleoli reappear. Cytokinesis Cytoplasm divides forming two new daughter cells. In plant cells, a cell plate appears at the equatorial plane. This plate grows from the centre towards the periphery forming two new daughter cells. MEIOSIS: Meiosis consists of two successive divisions: meiosis I and meiosis II. Meiosis I: Meiosis I is a reduction division. In this division, the chromosome number is reduced to half (n). Meiosis I is divided into four phases: Prophase I : It is the longest phase and consists of five sub-stages. Leptotene or Leptonema : The chromatin network condenses. Chromosomes are visible and they appear as beaded structures. Centrioles duplicate and start moving towards the opposite poles. Zygotene or Zygonema: Pairing of homologous chromosomes, i.e. synapse occurs. Here, pairing occurs between one paternal and one maternal chromosome. Pachytene or Pachynema : Four chromatids (two from each chromosome) are visible, and the structure is known as a tetrad . Chromosomes remain paired up at points called chiasmata . Exchange of genetic material occurs between two non-sister chromatids. This process is known as crossing-over . Diplotene or Diplonema : Homologous chromosomes repel and go away from each other except at chiasmata. Diakinesis:   Chiasmata become more visible. The nuclear membrane and nucleolus disappear. Formation of the spindle fibre begins. Anaphase I : Homologous chromosomes after crossing over start moving to the opposite poles. Telophase I : The nuclear membrane appears enclosing half set of chromosomes at each pole. Nucleoli reappear. Chromosomes change into long, thread-like chromatin fibres. Meiosis II: Meiosis II is a mitotic division. Each daughter cell formed in meiosis I further divides to form two identical cells. Thus, meiosis II results in the formation of four haploid daughter cells. All the sub-stages of meiosis II are same as the four phases of mitosis. Meiosis II is followed by Cytokinesis .

Thu August 21, 2014  

Ans: When crystals of certain salts are formed a definite number of molecules of water chemically combined in a definite proportion. Water of crystallization is water that is stoichiometrically bound into a crystal. Sodium carbonate deca hydrate or washing soda crystals (Na 2 CO 3 .10H 2 O) have 10 water molecules. The 10 water molecules are called water of crystallization.

Thu August 21, 2014  

Ans: Here space we space have space to space show space that space straight f left parenthesis straight x right parenthesis space is space both space one minus one space and space onto. For space one minus one comma straight f left parenthesis straight x right parenthesis equals straight x squared plus 4 comma space straight f left parenthesis straight y right parenthesis equals straight y squared plus 4 Now comma space for space straight f left parenthesis straight x right parenthesis space equals space straight f left parenthesis straight y right parenthesis rightwards double arrow straight x squared plus 4 equals straight y squared plus 4 rightwards double arrow straight x squared equals straight y squared rightwards double arrow straight x equals straight y because for space straight f left parenthesis straight x right parenthesis equals straight f left parenthesis straight y right parenthesis rightwards double arrow straight x equals straight y comma space therefore space straight f left parenthesis straight x right parenthesis space is space straight a space one minus one left parenthesis injective right parenthesis space function For space onto comma straight f left parenthesis straight x right parenthesis equals straight y rightwards double arrow straight x squared plus 4 equals straight y rightwards double arrow straight x squared equals straight y minus 4 rightwards double arrow straight x equals square root of straight y minus 4 end root Clearly space square root of straight y minus 4 end root space is space straight a space real space number space for space all space straight y greater than 4. Thus space for space all space straight y element of straight R comma space there space exists space straight x equals square root of straight y minus 4 end root space element of straight R comma space such space that straight f left parenthesis straight x right parenthesis equals straight f open parentheses square root of straight y minus 4 end root close parentheses equals open parentheses square root of straight y minus 4 end root close parentheses squared plus 4 equals straight y minus 4 plus 4 equals straight y This space shows space that space every space element space in space co minus domain space has space its space preimage space in space domain. Hence space straight f left parenthesis straight x right parenthesis space is space onto left parenthesis surjective right parenthesis. Thus space straight f left parenthesis straight x right parenthesis space is space both space one minus one space and space onto.

Wed August 20, 2014  

Ans: Acceleration is the rate of change of velocity with time.   Syntax error from line 1 column 78 to line 1 column 102. Unexpected '<mstyle '. Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.   The question you have asked require the use of a mathematical tool called "differentiation" .  The concept and details of differentiation will be introduced in the higher classes.

Wed August 20, 2014  

Ans:   From the above grpah, you can observe that given function is continuous everywhere.    So you need to observe that even non polynomial functions can also be continous.    Function  y  =  f ( x ) is continuous at point  x = a  if the following three conditions are satisfied : i.)  f ( a ) is defined , ii.) $ \displaystyle{ \lim_{ x \to a } \ f(x) } $ exists (i.e., is finite) , and iii.) $ \displaystyle{ \lim_{ x \to a } \ f(x) } = f(a) $ .

Wed August 20, 2014  

Ans: Yes. You are correct.    Mod z cant be negative in complex numbers. So you can remove square.

Wed August 20, 2014  

Ans: According to law of gravitation every objects of the universe attracts other objects. Force of attraction established between two objects is proportional to their masses. The moon revolving around the earth in certain orbit, centripetal gravitational force required for the orbital motion is provided to the moon by the gravitational pull of the earth. As in case of asteroids or meteoroids, they are smaller in mass than the earth, due to gravitational pull of earth they gets attracted either towards earths or other planets. Hence they fall directly towards the earth or other planets.

Wed August 20, 2014  

Ans: Any two bodies in the universe, attracts each other due to gravitaional force.  According to law of gravitation, moon follows straight line path, gets attracted towards the earth at every pont along its path, hence moon revolves around the earth, it dosen't fall towards earth. The same thing happens in case with other planets.

Wed August 20, 2014  

Ans: The treaty of Versailles was one of the peace treaties that ended the World War I between Germany and the Allied powers. It was signed on June 28, 1919. This treaty held Germany responsible for the First World War. According to this treaty, Germany had to pay huge war reparations to the victorious nations. This treaty is considered as one of the many causes which paved the way to the Second World War.   

Wed August 20, 2014  

Ans: Electromagnetic waves classified according to their frequency range: Radio waves:  Radio waves are used in ground wave propagation, sky wave propagation, television waves, commercial FM radio and used in cellular phones communication.   Microwave: Microwaves used in radar system, for cooking purposes. Microwaves are useful in communication because they can penetrate clouds, smoke, and light rain.   Infrared waves: Infrared waves are used in solar water heater, solar cooker, weather forecasting through infrared photography, for producing dehydrated fruits. It also used in green house effect to keep the plants warm. Visible light: Visible light emitted or reflected by everything which provides us information about the surrounding word. Ultraviolet rays: Ultraviolet rays are used to destroy bacteria and for sterilizing the surgical instruments, burglar alarm. These rays are also used to detect forged documents, finger print in forensic laboratory, preserve food stuff. X-rays: They can penetrate soft tissue like skin and muscle and are used to take X-ray pictures of bones in medicine.  γ-rays: Theses rays used in treatment of cancer and tumors, taking detailed images for diagnostic medicine. Gamma rays are produced in high energy nuclear explosions and supernovas.       

Tue August 19, 2014  

Ans: Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.

Tue August 19, 2014  

Ans: Kaiser Wilhelm II was ruling Germany before and during the First World War.   Kindly ask the other questions as seperate queries with the correct chapter name and standard.

Tue August 19, 2014  

Ans: Let 'u' be the initial velocity and 'a' be the uniform acceleration of the body.   Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.   Syntax error from line 1 column 49 to line 1 column 73. Unexpected '<mstyle '.

Tue August 19, 2014  

Ans: A magnetic needle is a bar magnet, and hence, it has a magnetic field around it.   The North Pole of the needle is the "North seeking pole" which tends to rotate towards the North of the Earth.   Similarly, the South Pole of the needle is the "South seeking pole" which tends to rotate towards the South of the Earth.

Tue August 19, 2014  

Ans: square root of 0.0169 end root equals 0.13  N o w space l e t s space f i n d space t h e space p e r c e n t a g e space o f space 0.0117 space i n space 0.13 fraction numerator 0.0117 over denominator 0.13 end fraction cross times 100 equals 117 over 13 equals 9 %

Tue August 19, 2014  

Ans: Strength: The strength of a solution is defined as the amount of a solute in grams present in one litre of the solution, and hence is expressed in g/litre and is usually written as g L -1 . Strength = Mass of the solute in grams / Volume of the solution in litres Normality: Normality of a solution is defined as the nuber of gram equivalent of the solute dissolved per litre of given solution. It is expressed by "N". N = Number of gram equivalent of solute / Volume of the solution in litres. N = Strength in grams per litre / Eq. mass of solute Ex. If eq. mass of sulphuric acid is 49 then, a solution of sulphuric acid having 0.49 gram of it dissolved in 350 ml of solution will have its normality as follows: N = (0.49 g / 49 g eq -1 ) x ( 1000 cm 3 L -1 /350cm 3 ) = 0.03 g eq L -1

Tue August 19, 2014  

Ans: So Area of Trapezium= Area of Rectangle + Area of Triangle   Use Heroins Formula to find Area of Triangle with sides 13, 14, 15   s equals fraction numerator 13 plus 14 plus 15 over denominator 2 end fraction equals 21 square root of 21 cross times 8 cross times 7 cross times 6 end root equals 7 cross times 3 cross times 4 equals 84 space s q. space m  A r e a space o f space T r i a n g l e space w i t h space b a s e space 15 space i s space g i v e n space b y 1 half cross times 15 cross times h e i g h t equals 84 h e i g h t equals 56 over 5 m  A r e a space o f space R e c tan g l e equals 56 over 5 cross times 10 equals 112 space s q. m  S o space a r e a space o f space t r a p e z i u m equals 84 plus 112 equals 196 space s q. space m
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