Recent questions tagged sec-e

Find the area of the region bounded by the curve $y^2 = x$ and the lines $x = 1, x = 4$ and the $x- axis.$

asked Dec 8, 2016 by priyanka.c

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How do plants and animals adapt to water scarcity?OR Explain briefly the ‘rivet popper hypothesis’ by Paul Ehrlich.

asked Dec 8, 2016 by meena.p

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What do the following represent in a given graph? Describe one evidence that decisively prove that birds have evolved from reptiles?a. If operation of natural selection makes peak higher and narrower.b. If peak shifts to right directionc. If two peaks are formed instead.OR By taking industrial melanism as an example, explain the concept of natural selection by evolution. What is the role of variation in evolution?

asked Dec 8, 2016 by meena.p

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Give a brief account of asexual reproduction . and Draw a labeled sketch of a L.S. of a pistil showing porogamous type of fertilization.

asked Dec 8, 2016 by meena.p

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Find the point on the curve $y = x^3 - 11 x + 5$ at which the target is $y = x -11.$

asked Dec 8, 2016 by priyanka.c

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The two equal sides of an isosceles triangle with fixed base b are decreasing at the rate of 3 cm per second. How fast is the area decreasing when the two equal sides are equal to the base ?

asked Dec 8, 2016 by priyanka.c

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Represent schematically and describe carbon cycle in an ecosystem.

asked Dec 7, 2016 by meena.p

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Colour blindness is a recessive trait. A couple with normal vision have two sons, one with colour blindness and one with a normal vision. If the couple had daughters, what proportion of them will have a normal vision? Explain with the help of a pedigree diagram.OR Where do transcription and translation take place in a prokaryotic cell? Describe the three steps in transcription.

asked Dec 7, 2016 by meena.p

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Give the term/reason a.Mechanism responsible for parturition. b.Role of oxytocin during expulsion of the baby out of uterus. c.Why do pellucida block the entry of additional sperm? d.Sperms cannot reach ovum without seminal plasma. e. All copulations do not lead to fertilization and pregnancy. or Describe various natural methods of contraception in human beings.

asked Dec 7, 2016 by meena.p

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The radius of a circle is increasing uniformly at the rate of 3 cm/s. How fast is the volume of the cube increasing when the edge is 10cm long ?

asked Dec 7, 2016 by priyanka.c

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The total revenue in Rupees received from the sales of $x$ units of a product is given by $Rx = 3x^2 + 36x +5$ . Find the marginal revenue , when $x=15$, where by marginal.

asked Dec 6, 2016 by priyanka.c

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If A and B are symmetric matrices, prove that AB - BA is a skew symmetric matrix

asked Dec 6, 2016 by priyanka.c

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Using cofactors of elements of second row, evaluate $\triangle = \begin{vmatrix} 5 & 3 & 8 \\ 2 & 0 & 1 \\ 1 & 2 & 3 \end{vmatrix}$

asked Dec 5, 2016 by priyanka.c

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Differentiate between regulators and conformers. Why do small animals do not show regulation?Represent schematically and describe the phosphorus cycle in an ecosystem.

asked Dec 5, 2016 by meena.p

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Explain chromosomal theory of inheritance.and Define mutations. Illustrate the type of mutations that arise by change in the chromosomal structure.

asked Dec 5, 2016 by meena.p

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Study the given diagram: a)Pick out and name the cells that undergo spermiogenesis. b)Name the cells ‘a’ and ‘b’. c)Give the ploidy level of ‘b’ and ‘e’. d)What are the cells marked as ‘f’? Mention their functions. e)Mention the cell division type in ‘a’ and ‘b’. and Briefly explain the various reproductive technologies to assist infertile couple to have children.

asked Dec 5, 2016 by meena.p

1 answer

Evaluate : $\tan^{-1} (1) + cos^{-1} ( \frac{-1}{2} )+ \sin^{-1} (\frac{-1}{2})$

asked Dec 5, 2016 by priyanka.c

2 answers

Describe the exponential growth model of a diagram along with a curve.and Describe the logistic growth model of population along with a suitable curve. Why is this curve more realistic?

asked Dec 2, 2016 by meena.p

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Describe the inheritance of the flower colour in snap dragon. Taking the examples of ABO blood group types of humans, explain the phenomenon of multiple alleles and co dominance.

asked Dec 2, 2016 by meena.p

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Distinguish between asexual reproduction and sexual reproduction. Why is vegetative reproduction also considered a type of asexual reproduction? Which is a better mode of reproduction: Sexual or Asexual. Why? Draw an embryo sac of the flowering plant and label (i) central cell (ii) chalazal end (iii) synergids. Name the cell that develops an embryo sac. Mention the role played by various cells of embryo sac.

asked Dec 2, 2016 by meena.p

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(a)Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why?

asked Nov 29, 2016 by meena.p

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(i) A chemical reaction $2A \to 4B + C$ in gas phase occurs in a closed vessel. The concentration of $B$ is found to increase by $5 \times 10^{-3}\; mol L^{-1}$ in $10$ seconds, Calculate (a) the rate of appearance of B (b) the rate of disappearance of A. (ii)The activation energy of first order reaction at $300\;K$ is $60 kJ/mol$ . In the presence of a catalyst, the activation energy gets lowered to $50 kJ/mol$ at $300K$. How many times the reaction rate changes in presence of a catalyst at the same temperature?(iii) Define Threshold energy and activation energy. How they are related?

asked Nov 29, 2016 by meena.p

1 answer

Explain giving reasons: (i) Transition metals and many of their compounds show paramagnetic behaviour. (ii) The enthalpies of atomisation of the transition metals are high. (iii) The transition metals generally form coloured compounds. (iv) Transition metals and their many compounds act as good catalyst.

asked Nov 29, 2016 by meena.p

1 answer

Explain the following observations: (i) The boiling point of ethanol is higher than that of methoxy methane. (ii) Phenol is more acidic than ethanol (iii) O-and -P - nitrophenols are more acidic than phenol . (iv) Phenol is an acid but does not react with sodium bicarbonate solution .

asked Nov 29, 2016 by meena.p

1 answer

(i) Why are complexes of the d-block elements coloured ? (ii) Why are scandium and Zinc not counted as transition metals even though they belong to the d-block? (iii)When a brown compound of manganers (A) is treated with $Hcl$ it gives a gas (B) . The gas taken in excess , reacts with $Nh_3$ to give an explosive compound A and B

asked Nov 29, 2016 by meena.p

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Distinguish between rate expression and rate constant of a reaction. (ii) Can a reaction have zero activation energy ? explain (iii) Is the enthalpy of a reaction altered by a catalyst

asked Nov 29, 2016 by meena.p

1 answer

If $y = \sin (m \sin^{-1} x),$ evaluate $(1-x) \frac{d^2y}{dx^2} - x \frac{dy}{dx} + m^2y = 0$

asked Nov 23, 2016 by priyanka.c

1 answer

Event A and B are such that $P(A) = \frac{1}{2}, P(B) = \frac{7}{12} $, P (not A or not B) =$ \frac{1}{4}$. State whether A and B are independent.

asked Nov 23, 2016 by priyanka.c

1 answer

If A, B, C are position vectors (2, 0, 0), (0, 1, 0) and (0, 0, 2) show that $\triangle ABC$ is isosceles .

asked Nov 23, 2016 by priyanka.c

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An aromatic compound 'A' on treatment with $CHCl_3/KOH$ gives two compounds 'B' and 'C'. Both B and C give the same product 'D' when distilled with zinc dust. oxidation of D gives E having molecular formula $C_7H_6O_2$. The sodium salt of E on heating with sodalime gives F which may also be obtained by distilling A with Zinc dust . Identify A to F

asked Nov 23, 2016 by meena.p

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Find the value of $\lambda$, so that the lines $\frac{1-x}{3} = \frac{7y - 14}{2 \lambda} = \frac{z-3}{2} \;and\; \frac{7-7 \lambda}{3 \lambda} = \frac{y-5}{1} = \frac{6-z}{5} $ are at right angle

asked Nov 22, 2016 by priyanka.c

1 answer

Find the value of 'a ' so that the function f(x) is defined by $f(x) = \begin{cases} \frac{\sin ^2 a x}{x^2} & x \neq 0 \\ 1 , & x =0 \end{cases}$ may be continuous at x = 0

asked Nov 22, 2016 by priyanka.c

1 answer

Use matrix method to examine if the following system of equation for consistency or inconsistency $4x - 2y = 3, \; \; 6x - 3y = 5$

asked Nov 22, 2016 by priyanka.c

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Assign reasons for the following: (i) The enthalpies of atomisation of transition elements are high. (ii) The transition metals and many of their compounds act as good catalysts. (iii) From element to element the actinoid contraction is greater than the lanthanoid contraction. (iv) The $E^{\circ}$ value for the $Mn ^{3+} / Mn ^{2+}$ couple is much more positive than that of $Cr^{3+} / Cr^{2+}.$ (v) Scandium $(z=21)$ does not exhibit variable oxidation states and yet it is regarded as a transition element

asked Nov 22, 2016 by meena.p

1 answer

Decomposition of phosphine $(PH_3)$ at $120^{\circ}C$ proceeds according to the equation: $4PH_3(g) \to P_4(g) + 6H_2(g)$ It is found that this reaction follows the following rate equation: Rate $= k[PH_3]$ The half-life of $PH_3$ is $37.9\;s$ at $120^{\circ}C.$ (i) How much time will be required for $\large\frac{3}{4}$ of $PH_3$ to decompose? (ii) What fraction of the original amount of $PH_3$ will remain undecomposed after 1 minute?

asked Nov 22, 2016 by meena.p

1 answer

If $|\overrightarrow{a}| = 11, |\overrightarrow {b} | = 23 and |\overrightarrow {a} - \overrightarrow {b} |= 30 $

asked Nov 22, 2016 by priyanka.c

1 answer

Solve the differential equation $\frac{dy}{dx} = log (x+1)$

asked Nov 22, 2016 by priyanka.c

1 answer

$\begin{align}\int_0^\frac{\pi}{2} \frac{\sin x}{1 + \cos^2 x } dx \end{align}$

asked Nov 22, 2016 by priyanka.c

1 answer

Without expanding evaluate: $\begin{vmatrix} \frac{1}{a} & a^2 & bc \\ \frac{1}{b} & b^2 & ca \\ \frac{1}{c} & c^2 & ab \end{vmatrix}$

asked Nov 22, 2016 by priyanka.c

1 answer

Evaluate : $\tan \frac{1}{2} (\cos^{-1} \frac{\sqrt 5}{3})$

asked Nov 22, 2016 by priyanka.c

1 answer

Verify Rolle's theorem for $f(x) = x^2 + 2$ in the interval [-2,2]

asked Nov 21, 2016 by priyanka.c

1 answer

differentiate $y = (\sin x)^x + \sin^{-1} \sqrt x$

asked Nov 21, 2016 by priyanka.c

1 answer

Using elementary row transformation, find the inverse of $A = \begin{bmatrix} 2 & -6 \\ 1 & -2\end{bmatrix}$

asked Nov 21, 2016 by priyanka.c

1 answer

If $P(A) = 0.25, P(B) = 0.4 \; and \; P (A \cup B) = 0.5 \; find \; P (A \cap B) \;and \; P (A \cap \bar{B})$

asked Nov 21, 2016 by priyanka.c

1 answer

Are the vectors $(\hat {i} + \hat{j} + \hat{k}), (2\hat{i} +3\hat{j} -\hat{k})$ and $(-\hat{i} -2\hat{j} +2 \hat{k})$ are linearly dependent ?

asked Nov 21, 2016 by priyanka.c

1 answer

A car stands from a point P at time t = 0 sec and stops at point Q. The distance x, in metres, covered by it, in t seconds in given by $x = t^2 (2 - \frac{t}{3})$. Find the time taken by it to reach Q and also find the distance between P and Q.

asked Nov 21, 2016 by priyanka.c

1 answer

Find the point at which the target to the curve $y = \sqrt{4x-3} - 1$ has its slope $\frac{2}{3}$

asked Nov 21, 2016 by priyanka.c

1 answer

Solve the system of equation $2x + 5y = 1 \; \ \; \; and \; \; \; \; 3x + 2y = 7$

asked Nov 20, 2016 by priyanka.c

1 answer

Find X and Y, if $X + Y= \begin{bmatrix} 5 & 2 \\ 0 & 9 \end{bmatrix}$ and $X - Y = \begin{bmatrix} 3 & 6 \\ 0 & -1 \end{bmatrix}$

asked Nov 20, 2016 by priyanka.c

1 answer

Evaluate $tan^{-1} (\frac{\cos x}{1-\sin x}), \;\; \; -\frac{\pi}{2} < x < \frac{\pi}{2}$

asked Nov 20, 2016 by priyanka.c

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