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Wed Apr 16, 2014 11:30 am  

Ans: Action and reaction pair always act on two different objects that are in contact. They have equal magnitude and always act in the opposite directions.   Hence, (A), (B) and (C) are correct and (D) is incorrect.

Wed Apr 16, 2014 8:09 am  

Ans: (i) 5 x minus 2 over 3 minus 7 x minus 1 greater than x over 4 minus 2 x minus 5 over 3 greater than x over 4 minus 5 over 3 greater than fraction numerator 9 x over denominator 4 end fraction x less than minus 20 over 27 rightwards double arrow x space element of left parenthesis minus infinity comma minus 20 over 27 right parenthesis       (ii) 2 x minus 3 over 4 plus 8 greater or equal than 2 plus fraction numerator 4 x over denominator 3 end fraction fraction numerator 2 x over denominator 3 end fraction greater or equal than minus 21 over 4 x greater or equal than minus 63 over 8 rightwards double arrow x element of left square bracket minus 63 over 8 comma infinity right square bracket

Wed Apr 16, 2014 7:45 am  

Ans: There are no certainties in any examination as to which questions might come, however the following derivations are very important from the exam point of view:   1) Expression of current density in the form of Ohm's law 2) Equivalent resistance of a combination of resistors in series or parallel 3) The balance condition in a wheatstone bridge 4) Internal resistance of a cell by potentiometer

Wed Apr 16, 2014 7:42 am  

Ans: The questions in the subjective section help understanding and learning the concepts of that chapter. Hence, they prepare you well for all the possible questions that might come in the exam.   These questions will help you encounter questions that come in the exam in the best possible manner that you can, and hence will help you score well in your exams.

Wed Apr 16, 2014 12:06 am  

Ans: (A) When the resultant force decreases, the object might still be accelerating. However, it will be negative acceleration.   (B) When the velocity changes direction, the acceleration changes. Hence, the body is said to be accelerating.   (C) When the resultant force on an object is zero, the acceleration is zero in accordance with Newton's second law a = F/m.   (D) When the resultant force is at right angles to the direction of motion, the body is still accelerating (as in the case of circular motion).   Hence, the correct option is C.

Tue Apr 15, 2014 11:03 pm  

Ans: The

Tue Apr 15, 2014 10:46 pm  

Ans: The emission of electrons by chlorophyll takes place due to the absorption of light energy by the chlorophyll. Emitted electron are sent further in electron transport system and also used up during photolysis of water and also for the formation of ATP molecule. Photolysis of water is important because the hydrogen released from the water molecule reduces NAD to NADH 2 . NADH 2 acts as a hydrogen donor at the time of conversion of carbon dioxide into glucose.

Tue Apr 15, 2014 8:12 pm  

Ans: There is no such number infinity.   It represents a quantity which has no end.   It is not a real number and has no measure.   Division is a subsequent subtraction.   Suppose 12 over 3 open parentheses open parentheses open parentheses open parentheses 12 minus 3 close parentheses minus 3 close parentheses minus 3 close parentheses minus 3 close parentheses equals 0   Now consider 10 over 0 T h u s space w e space c a n space s u b t r a c t space 0 space f r o m space 10. 10 minus 0 minus 0 minus 0 minus 0 minus....... T h e space a b o v e space e q u a t i o n space n e v e r space e q u a l space t o space z e r o. H e n c e space w e space h a v e comma 10 over 0 equals infinity

Tue Apr 15, 2014 7:34 pm  

Ans: There are millions of plant and animal species found in our surroundings.  It would be difficult to give the scientific names of all these plants and animals. So, we request you to provide us with exact the list of plants and animals so that we are in a better position to answer your query. Scientific names of some common plants and animals is as follows: ANIMALS PLANTS Man Homo sapiens Peepal Ficus religiosa Cat Felis domesticus Mango Mangifera indica Dog Canis familiaris Potato Solanun tuberosum Honeybee Apis indica China rose Hibiscus rosa-sinensis Housefly Musca domestica Okra (Bhindi) Hibiscus esculentus Peacock Pavo cristatus Pineapple Ananas comosus Cobra Naja naja Pigeon pea (Arhar) Cajanus cajan Hoopoe Upapa epops Lentil (Masur) Lens esculenta

Tue Apr 15, 2014 6:54 pm  

Ans: This condition is called blighted ovum. It is caused due to several reasons: 1. Structural abnormalities in chromosomes. 2. Poor quality of sperm or ovum. 3. Abnormal cell division

Tue Apr 15, 2014 6:34 pm  

Ans: Answer : (A) , (B) and (D) Properties of Ionic solids: They are anisotropic in nature. They have high melting points. Conduct electricity in molten state.

Tue Apr 15, 2014 4:05 pm  


Tue Apr 15, 2014 3:42 pm  

Ans: The electrostatic potential at a point in an electric field may be defined as the amount of work done per unit test charge in moving it from infinity to that point against the electrostatic force.     The electrostatic potential energy of a system of point charges is defined as the work required to be done to bring the charges constituting the system to their respective locations from infinity.  

Tue Apr 15, 2014 1:11 pm  


Tue Apr 15, 2014 11:13 am  


Tue Apr 15, 2014 11:06 am  

Ans: This problem is based on Binomial Distribution. Let x = getting success According to given condition, an experiment succeeds thrice as often it fails. Thus, we have   p equals 3 over 4 comma space q equals 1 fourth space a n d space n space equals space 5 Error identifier "subscript" not found in transformation rule: SINGLEPOSTSCRIPT Thus, P(at least 3 successes) = P(X = 3) + P(X = 4) + P(X = 5)   Error identifier "subscript" not found in transformation rule: SINGLEPOSTSCRIPT  

Tue Apr 15, 2014 10:38 am  

Ans: How many water will be obtained by passing H2 over hot 1.970 g CuO. H 2       +     CuO    →      H 2 O    +       Cu                   1 mol            1 mol            1 mol CuO = 79.5 g CuO 1.970 g CuO = 0.0248  moles CuO As 1 mol of CuO produces 1 mol of H 2 O, hence 0.0248 moles of CuO produces 0.0248 moles of H 2 O. Now 18 g H 2 O = 1 mol 0.0248 moles of H 2 O = 0.446 g Thus, 1.970 g of CuO will produce 0 .0248 moles   or 0.446 g of H 2 O.

Tue Apr 15, 2014 10:36 am  

Ans: CaCO 3 + 2HCL → CaCl 2 + CO 2 + H 2 O 1 mol       2 moles   20 % HCl contains 20 g HCl in 100 g water 1 mol CaCO 3   = 100 g 50 g CaCO 3 = 0.5 moles CaCO 3 0.5 mole CaCO 3 correspond to 1 mol HCl 1 mol HCl = 36.5 g HCl 20 g HCl in 100 g water 36.5 g HCl = 182.5 g H 2 O Hence, 182.5 g solution of 20 % HCl is required.

Mon Apr 14, 2014 9:27 pm  

Ans: Dear aniket

Thanks for asking us a question in Ask the Expert section of TopperLearning.com.
If you are really interested in doing mathematics, take Maths as your additional subject and ofcourse it is necessary to pass all the subjects.

Topperlearning Team.

Mon Apr 14, 2014 9:18 pm  

Ans: You can take maths as an alternative subject along with PCB. According to the CBSE Guidelines, it is mandatory to get through in any 5 subjects. So if you take mathematics as an alternative subsject and if it is one the five subjects chosen by you then it is mandatory for you to pass in maths.
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