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JEE Main 2020 (08 Jan Shift 1)

2020 · 75 questions · First 10 Solutions Free
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Q1 mcq
A particle of mass $m$ is fixed to one end of a light spring having force constant $k$ and unstretched length $l.$ The other end is fixed. The system is given an angular speed $\omega$ about the fixed end of the spring such that it rotates in a circle in gravity free space. Then the stretch in the spring is:
a.
$\frac{ml\omega ^{2}}{k-\omega m}$
b.
$\frac{ml\omega ^{2}}{k-m\omega ^{2}}$ Correct Answer
c.
$\frac{ml\omega ^{2}}{k+m\omega ^{2}}$
d.
$\frac{ml\omega ^{2}}{k+m\omega}$

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Q2 mcq
Effective capacitance of parallel combination of two capacitors $C_{1}$ and $C_{2}$ is $10$ $\mu$ $F.$ When these capacitors are individually connected to a voltage source of $1V,$ the energy stored in the capacitor $C_{2}$ is $4$ times that of $C_{1}.$ If these capacitors are connected in series, their effective capacitance will be:
a.
$4.2$ $\mu$ $F$
b.
$3.2$ $\mu$ $F$
c.
$1.6$ $\mu$ $F$ Correct Answer
d.
$8.4$ $\mu$ $F$

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Q3 mcq
When photon of energy $4.0eV$ strikes the surface of a metal $A,$ the ejected photoelectrons have maximum kinetic energy $T_{A}eV$ and de-Broglie wavelength $\lambda _{A}.$ The maximum kinetic energy of photoelectrons liberated from another metal $B$ by photon of energy $4.50eV$ is $T_{B} = (T_{A}-1.5)eV.$ If the de-Broglie wavelength of these photoelectrons $\lambda _{B} = 2\lambda _{A},$ then the work function of metal $B$ is:
a.
$4eV$ Correct Answer
b.
$2eV$
c.
$1.5eV$
d.
$3eV$

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Q4 mcq
The plot that depicts the behavior of the mean free time $Ο„$ (time between two successive collisions) for the molecules of an ideal gas, as a function of temperature $(T),$ qualitatively, is: (Graphs are schematic and not drawn to scale)
Question 4 image

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Q5 mcq
The coordinates of the centre of mass of a uniform flag-shaped lamina (thin flat plate) of mass $4\,kg$ . (The coordinates of the same are shown in the figure) are:
Question 5 image
a.
$(1.25\,m, 1.50\,m)$
b.
$(0.75\,m, 1.75\,m)$ Correct Answer
c.
$(0.75\,m, 0.75\,m)$
d.
$(1\,m, 1.75\,m)$

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Q6 mcq
Consider two solid spheres of radii $R_{1} = 1\,m$ , $R_{2} = 2\,m$ and masses $M_{1}$ and $M_{2},$ respectively. The gravitational field due to sphere $(1)$ and $(2)$ are shown. The value of $\frac{M}{M_{2}}^{1}$ is:
Question 6 image
a.
$\frac{2}{3}$
b.
$\frac{1}{6}$ Correct Answer
c.
$\frac{1}{2}$
d.
$\frac{1}{3}$

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Q7 mcq
$|$ $|$ $|$ At time $t= 0$ magnetic field of $1000\,Gauss$ is passing perpendicularly through the area defined by the closed loop shown in the figure. If the magnetic field reduces linearly to $500\,Gauss,$ in the next $5s,$ then induced $EMF$ in the loop is:
Question 7 image
a.
$56$ $\mu$ $V$ Correct Answer
b.
$28$ $\mu$ $V$
c.
$48$ $\mu$ $V$
d.
$36$ $\mu$ $V$

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Q8 nat
A body $A$ of mass $m= 0.1\,kg$ has an initial velocity of $3Λ†i\,m\,s^{-1}$ . It collides elastically with another body $B$ of the same mass which has an initial velocity of $5Λ†j\,m\,s^{-1}$ . After the collision, $A$ moves with a velocity $\vec{v}= 4(Λ†i +Λ†j)\,m\,s^{-1}$ . The energy of $B$ after the collision is written as $\frac{x}{10}\,J$ . The value of $x$ is
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Q9 mcq
Boolean relation at the output stage- $Y$ for the following circuit is:
Question 9 image
a.
$- -$ $A + B$
b.
$A+B$
c.
$A\cdot B$
d.
$- -$ $A \cdot B$ Correct Answer

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Q10 mcq
The dimension of stopping potential $V_{0}$ in photoelectric effect in units of Planck’s constant β€˜ $h$ ’, speed of light β€˜ $c$ ’ and Gravitational constant β€˜ $G$ ’ and ampere $A$ is:
a.
$h \frac{1}{3}G\frac{2}{3}c\frac{1}{3}A^{-1}$
b.
$h^{0}c^{5}G^{-1}A^{-1}$ Correct Answer
c.
$h^{-}\frac{2}{3}c^{-}\frac{1}{3}G \frac{4}{3}A^{-1}$
d.
$h^{2}G\frac{3}{2}c\frac{1}{3}A^{-1}$

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Q11 mcq
A thermodynamic cycle $xyzx$ is shown on a $V$ - $T$ diagram. The $P$ - $V$ diagram that best describes this cycle is: (Diagrams are schematic and not to scale)
Question 11 image
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Q12 mcq
Consider a uniform rod of mass $M = 4m$ and length $l$ pivoted about its centre. A mass $m$ moving with velocity $v$ making angle $\theta = \frac{\pi}{4}$ to the rod’s long axis collides with one end of the rod and sticks to it. The angular speed of the rod-mass system just after the collision is:
a.
$\frac{3}{7\sqrt{2}} \frac{v}{l}$
b.
$\frac{3}{7} \frac{v}{l}$
c.
$\frac{3\sqrt{2}}{7} \frac{v}{l}$
d.
$\frac{4}{7} \frac{v}{l}$
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Q13 mcq
A leak proof cylinder of length $1\,m,$ made of a metal which has very low coefficient of expansion is floating vertically in water at $0^{o}C$ such that its height above the water surface is $20\,cm.$ When the temperature of water is increased to $4^{o}C,$ the height of the cylinder above the water surface becomes $21\,cm.$ The density of water at $T = 4^{o}C,$ relative to the density at $T = 0^{o}C$ is close to:
a.
$1.26$
b.
$1.04$
c.
$1.01$
d.
$1.03$
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Q14 mcq
The graph which depicts the results of Rutherford gold foil experiment with $\alpha$ -particles is: $\theta :$ Scattering angle $Y :$ Number of scattered $\alpha$ -particles detected (Plots are schematic and not to scale)
Question 14 image
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Q15 nat
A one metre long (both ends open) organ pipe is kept in a gas that has double the density of air at STP. Assuming the speed of sound in air at STP is $300\,m/s,$ the frequency difference between the fundamental and second harmonic of this pipe is __________ Hz.
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Q16 nat
A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is $30\,cm$ and the refractive index of the lens material is $1.5,$ then the focal length of the lens (in cm) is ___________.
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Q17 nat
Four resistances of $15\,\Omega , \,12\,\Omega , \,4\,\Omega$ and $10\,\Omega$ respectively in cyclic order to form Wheatstone’s network. The resistance that is to be connected in parallel with the resistance of $10\,\Omega$ to balance the network is ______________ $\Omega .$
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Q18 mcq
In finding the electric field using Gauss law the formula $\vec{E} = \frac{q_{enc}}{$\epsilon$_{0}|A|}$ is applicable. In the formula $\epsilon$ $_{0}$ is permittivity of free space, $A$ is the area of Gaussian surface and $q_{enc}$ is charge enclosed by the Gaussian surface. This equation can be used in which of the following situation?
a.
Only when the Gaussian surface is an equipotential surface
b.
Only when the Gaussian surface is an equipotential surface and $\vec{E}$ is constant on the surface.
c.
Only when $\vec{E} =$ constant on the surface.
d.
For any choice of Gaussian surface.
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Q19 mcq
Three charged particles $A ,\, B$ and $C$ with charges $-4q, 2q$ and $-2q$ are present on the circumference of a circle of radius $d.$ The charged particles $A, C$ and centre $O$ of the circle formed an equilateral triangle as shown in the figure. The electric field at the point $O$ is
Question 19 image
a.
$\frac{\sqrt{3}q}{\pi \epsilon _{0}d^{2}}$
b.
$\frac{2\sqrt{3}q}{\pi \epsilon _{0}d^{2}}$
c.
$\frac{\sqrt{3}q}{4\pi \epsilon _{0}d^{2}}$
d.
$\frac{3\sqrt{3}q}{4\pi \epsilon _{0}d^{2}}$
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Q20 mcq
The magnifying power of a telescope with tube length $60cm$ is $5.$ What is the focal length of its eye piece?
a.
$20cm$
b.
$40cm$
c.
$30cm$
d.
$10cm$
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Q21 mcq
The critical angle of a medium for a specific wavelength, if the medium has relative permittivity $3$ and relative permeability $\frac{4}{3}$ for this wavelength, will be:
a.
$15^{o}$
b.
$30^{o}$
c.
$45^{o}$
d.
$60^{o}$
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Q22 mcq
Consider a solid sphere of radius $R$ and mass density $\rho (r) =\rho _{0}(1 - \frac{r^{2}}{R^{2}}), 0 <r\leq R.$ The minimum density of a liquid in which it will float is:
a.
$\frac{\rho _{0}}{3}$
b.
$\frac{\rho _{0}}{5}$
c.
$\frac{2\rho _{0}}{5}$
d.
$\frac{2\rho _{0}}{3}$
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Q23 nat
A particle is moving along the $x$ -axis with its coordinate with time $t$ given by $x(t) = 10 + 8t-3t^{2}.$ Another particle is moving along the $y$ -axis with its coordinate as a function of time given by $y(t) = 5 -8t^{3}.$ At $t= 1\,s,$ the speed of the second particle as measured in the frame of the first particle is given as $\sqrt{v}.$ Then $v(in\,m\,s^{-1})$ is ___________.
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Q24 mcq
The length of a potentiometer wire is $1200\,cm$ and it carries a current of $60\,mA$ For a cell of $emf\,5\,V$ and internal resistance of $20\,\Omega$ the null point on it is found to be at $1000\,cm$ The resistance of whole wire is:
a.
$80\Omega$
b.
$120\Omega$
c.
$60\Omega$
d.
$100\Omega$
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Q25 mcq
Proton with kinetic energy of $1\,MeV$ moves from south to north. It gets an acceleration of $10^{12}\,m/s^{2}$ by an applied magnetic field (west to east). The value of magnetic field: (Rest mass of proton is $1.6 \times 10^{-27}kg$ )
a.
$0.71mT$
b.
$7.1mT$
c.
$0.071mT$
d.
$71mT$
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Q26 nat
The magnitude of work done by a gas that undergoes a reversible expansion along the path $ABC$ shown in the figure is _________.
Question 26 image
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Q27 mcq
The strength of an aqueous $NaOH$ solution is most accurately determined by titrating: (Note: consider that an appropriate indicator is used)
a.
$Aq. NaOH$ in a pipette and aqueous oxalic acid in a burette
b.
$Aq. NaOH$ in a burette and aqueous oxalic acid in a conical flask
c.
$Aq. NaOH$ in a burette and concentrate $H_{2}SO_{4}$ in a conical flask
d.
$Aq. NaOH$ in a volumetric flask and concentrated $H_{2}SO_{4}$ in a conical flask
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Q28 nat
The volume $(in\,mL)$ of $0.125\,M\,AgNO_{3}$ required to quantitatively precipitate chloride ions in $0.3g$ of $[Co(NH_{3})_{6}]Cl_{3}$ is __________. $^{M}[Co(NH_{3})_{6}]Cl_{3} = 267.46g/mol$ $^{M}AgNO_{3} = 169.87g/mol$ Report the nearest integer as the answer.
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Q29 mcq
As per Hardy-Schulze formulation, the flocculation values of the following for ferric hydroxide sol are in the order:
a.
$K_{3}[Fe(CN)_{6}] < K_{2}CrO_{4} <KBr=KNO_{3} = AlCl$
b.
$K_{3}_{3}[Fe(CN)_{6}] < K_{2}CrO_{4} <AlCl_{3} <KBr<KNO_{3}$
c.
$AlCl_{3} > K_{3}[Fe(CN)_{6}] > K_{2}CrO_{4} >KBr=KN$
d.
$OK_{3}_{3}[Fe(CN)_{6}] >AlCl_{3} > K_{2}CrO_{4} >KBr>KNO_{3}$
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Q30 mcq
The complex that can show $fac$ - and $mer$ -isomers is:
a.
$[Co(NH_{3})_{4}Cl_{2}]^{+}$
b.
$[Pt(NH_{3})_{2}Cl_{2}]$
c.
$[CoCl_{2}(en)_{2}]$
d.
$[Co(NH_{3})_{3}(NO_{2})_{3}]$
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Q31 mcq
The major products $A$ and $B$ in the following reactions are
Question 31 image
a.
and
b.
and
c.
and
d.
and
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Q32 nat
Ferrous sulphate heptahydrate is used to fortify foods with iron. The amount (in grams) of the salt required to achieve $10ppm$ of iron in $100kg$ of wheat is ____________. Atomic weight: $Fe = 55.85; S = 32.00; O = 16.00$
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Q33 mcq
The third ionization enthalpy is minimum for:
a.
$Co$
b.
$Fe$
c.
$Ni$
d.
$Mn$
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Q34 mcq
When gypsum is heated to $393K,$ it forms:
a.
Anhydrous $CaSO_{4}$
b.
$CaSO_{4}\cdot 5H_{2}O$
c.
$CaSO_{4}\cdot 0.5H_{2}O$
d.
Dead burnt plaster
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Q35 nat
What would be the electrode potential for the given half-cell reaction at $pH = 5? _________.$ $2H_{2}O \rightarrow O\rightarrow_{2}+ 4H + 4e^{\oplus }^{-}; E^{0}_{red} = 1.23V$ $(R = 8.314Jmol^{-1}K^{-1}; Temp = 298K; oxygen\,under\,s tan dard\,. atm. pressureof1bar)$
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Q36 mcq
The predominant intermolecular forces present in ethyl acetate, a liquid, are:
a.
London dispersion and dipole-dipole
b.
hydrogen bonding and London dispersion
c.
Dipole-dipole and hydrogen bonding
d.
London dispersion, dipole-dipole and hydrogen bonding
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Q37 mcq
Which of the following statement is not true for glucose?
a.
Glucose exists in two crystalline forms $\alpha$ and $\beta$
b.
Glucose gives Schiff’s test for aldehyde
c.
Glucose reacts with hydroxylamine to form oxime
d.
The pentaacetate of glucose does not react with hydroxylamine to give oxime
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Q38 mcq
The stoichiometry and solubility product of a salt with the solubility curve given below is, respectively:
Question 38 image
a.
$X_{2}Y, 2 \times 10^{-9}M^{3}$
b.
$XY_{2}, 4 \times 10^{-9}M^{3}$
c.
$XY_{2}, 1 \times 10^{-9}M^{3}$
d.
$XY, 2 \times 10^{-6}M^{3}$
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Q39 mcq
The first ionization energy (in $kJ/mol$ ) of $Na, \,Mg, \,Al$ and $Si$ respectively are:
a.
$496, 737, 577, 786$
b.
$496, 577, 737, 786$
c.
$786, 737, 577, 496$
d.
$496, 577, 786, 737$
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Q40 nat
The number of chiral centres in penicillin is _________.
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Q41 mcq
For the Balmer series, in the spectrum of $H$ atom, $^{-}v = R_{H}{\frac{1}{n^{2}_{1}} - \frac{1}{n^{2}_{2}}},$ the correct statements among $(I)$ to $(IV)$ are, $(I)$ As wavelength decreases, the lines in the series converge. $(II)$ The integer $n_{1}$ is equal to $2$ / $(III)$ The lines of the longest wavelength correspond to $n_{2} = 3$ . $(IV)$ The ionization energy of hydrogen can be calculated from the wave number of these lines.
a.
$(I), (III), (IV)$
b.
$(I), (II), (III)$
c.
$(I), (II), (IV)$
d.
$(II), (III), (IV)$
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Q42 mcq
Arrange the following compounds in increasing order of $C -OH$ bond length: methanol, phenol, $p$ - ethoxyphenol
a.
methanol $< p$ -ethoxyphenol $<$ phenol
b.
phenol $<$ methanol $< p$ -ethoxyphenol
c.
phenol $< p$ -ethoxyphenol $<$ methanol
d.
methanol $<$ phenol $< p$ -ethoxyphenol
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Q43 mcq
The decreasing order of reactivity towards dehydrohalogenation $(E_{1})$ reaction of the following compounds is:
Question 43 image
a.
$D >B>C >A$
b.
$B >D>A>C$
c.
$B >D>C >A$
d.
$B >A>D>C$
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Q44 mcq
A graph of vapour pressure and temperature for three different liquids $X, Y$ and $Z$ is shown below: The following inferences are made: $(A)X$ has higher intermolecular interactions compared to $Y.$ $(B)X$ has lower intermolecular interactions compared to $Y.$ $(C)Z$ has lower intermolecular interactions compared to $Y.$ The correct inferences is/are:
Question 44 image
a.
$(A)$ and $(C)$
b.
$(A)$
c.
$(B)$
d.
$(C)$
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Q45 mcq
A flask contains a mixture of isohexane and $3$ -methylpentane. One of the liquids boils at $63^{o}C$ while the other boils at $60^{o}C.$ What is the best way to separate the two liquids and which one will be distilled out first?
a.
fractional distillation, isohexane
b.
simple distillation, $3$ -methylpentane
c.
simple distillation, isohexane
d.
fractional distillation, $3$ -methylpentane
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Q46 mcq
The rate of a certain biochemical reaction at physiological temperature $(T)$ occurs $10^{6}$ times faster with enzyme than without. The change in the activation energy upon adding enzyme is:
a.
$-6(2.303)RT$
b.
$-6RT$
c.
$+6(2.303)RT$
d.
$+6RT$
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Q47 mcq
The major product of the following reaction is:
Question 47 image
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Q48 mcq
The most suitable reagent for the given conversion is:
Question 48 image
a.
$B_{2}H_{6}$
b.
$NaBH_{4}$
c.
$LiAlH_{4}$
d.
$H_{2}/Pd$
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Q49 mcq
Among the gases $(a) -(e),$ the gases that cause greenhouse effect are: $(a)CO_{2}$ $(b)H_{2}O$ $(c)CFCs$ $(d)O_{2}$ $(e)O_{3}$
a.
$(a), (b), (c)$ and $(d)$
b.
$(a), (b), (c)$ and $(e)$
c.
$(a)$ and $(d)$
d.
$(a), (c), (d)$ and $(e)$
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Q50 mcq
The number of bonds between sulphur and oxygen atoms in $S_{2}O^{2-}_{8}$ and the number of bonds between sulphur and sulphur atoms in rhombic sulphur, respectively are:
a.
$4$ and $6$
b.
$8$ and $8$
c.
$8$ and $6$
d.
$4$ and $8$
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Q51 nat
Let the normal at a point $P$ on the curve $y^{2} -3x^{2} +y+ 10 = 0$ intersect the $y$ -axis at $(0, \frac{3}{2}).$ If $m$ is the slope of the tangent at $P$ to the curve, then $|m|$ is equal to ___________.
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Q52 mcq
If the equation $x^{2} +bx+ 45 = 0, \,b\in R$ has conjugate complex roots and they satisfy $|z+ 1| = 2\sqrt{10},$ then
a.
$b^{2} - b= 30$
b.
$b^{2} +b= 72$
c.
$b^{2} - b= 42$
d.
$b^{2} +b= 12$
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Q53 mcq
$_{x}lim_{\rightarrow 0\rightarrow } (\frac{3x^{2}+2}{7x^{2}+2} ) \frac{1}{x2}$ is equal to
a.
$\frac{1}{e}$
b.
$\frac{1}{e^{2}}$
c.
$e^{2}$
d.
$e$
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Q54 nat
The number of all $3 \times 3$ matrices $A,$ with entries from the set ${-1, 0, 1}$ such that the sum of the diagonal elements of $AA^{T}$ is $3,$ is ___________.
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Q55 mcq
Let $f(x) =(sin(tan^{-1} x)+ sin(cot^{-1} x))^{2} -1$ , $|x| > 1$ . If $\frac{dy}{dx} = \frac{1}{2} \frac{d}{dx}(sin^{-1}(f(x)))$ and $y(\sqrt{3})= \frac{\pi}{6},$ then $y(-\sqrt{3})$ is equal to:
a.
$\frac{2\pi}{3}$
b.
$- \frac{\pi}{6}$
c.
$\frac{5\pi}{6}$
d.
$\frac{\pi}{3}$
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Q56 mcq
The locus of a point which divides the line segment joining the point $(0, -1)$ and a point on the parabola $x^{2} = 4y$ internally in the ratio $1 : 2$ is:
a.
$9x^{2} -12y= 8$
b.
$9x^{2} -3y= 2$
c.
$x^{2} -3y= 2$
d.
$4x^{2} -3y= 2$
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Q57 mcq
Let $A$ and $B$ be two independent events such that $P(A) = \frac{1}{3}$ and $P(B) = \frac{1}{6}.$ Then, which of the following is true?
a.
$P(\frac{A}{B})= \frac{2}{3}$
b.
$P(\frac{A}{B'})= \frac{1}{3}$
c.
$P(\frac{A'}{B'})= \frac{1}{3}$
d.
$P(\frac{A}{(A\cup B)})= \frac{1}{4}$
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Q58 mcq
For $a> 0,$ let the curves $C_{1} :y^{2} =ax$ and $C_{2} :x^{2} =ay$ intersect at origin $O$ and a point $P.$ Let the line $x=b(0 <b<a)$ intersect the chord $OP$ and the $x$ -axis at points $Q$ and $R,$ respectively. If the line $x=b$ bisects the area bounded by the curves, $C_{1}$ and $C_{2},$ and the area of $\Delta OQR= \frac{1}{2} ,$ then β€˜ $a$ ’ satisfies the equation:
a.
$x^{6} -6x^{3} + 4 = 0$
b.
$x^{6} -12x^{3} + 4 = 0$
c.
$x^{6} + 6x^{3} -4 = 0$
d.
$x^{6} -12x^{3} -4 = 0$
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Q59 nat
The least positive value of β€˜ $a$ ’ for which the equation, $2x^{2} + (a-10)x+ \frac{33}{2} = 2a$ has real roots is ___________.
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Q60 mcq
Which one of the following is a tautology?
a.
$(p\wedge (p q)) \rightarrow \rightarrow q$
b.
$q\rightarrow (\rightarrow p\wedge (p\rightarrow \rightarrow q))$
c.
$p\wedge (p\vee \vec{q})$
d.
$p\vee (p\wedge q)$
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Q61 mcq
If $a,b$ and $c$ are the greatest values of $^{19}C_{p},^{20}C_{q}$ and $^{21}C_{r}$ respectively, then:
a.
$\frac{a}{11} = \frac{b}{22} = \frac{c}{21}$
b.
$\frac{a}{10} = \frac{b}{11} = \frac{c}{21}$
c.
$\frac{a}{11} = \frac{b}{22} = \frac{c}{42}$
d.
$\frac{a}{10} = \frac{b}{11} = \frac{c}{42}$
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Q62 mcq
Let the line $y=mx$ and the ellipse $2x^{2} +y^{2} = 1$ intersect at a point $P$ in the first quadrant. If the normal to this ellipse at $P$ meets the co-ordinate axes at $(- \frac{1}{3\sqrt{2}}, 0)$ and $(0,\beta )$ , then $\beta$ is equal to
a.
$\frac{2\sqrt{2}}{3}$
b.
$\frac{2}{\sqrt{3}}$
c.
$\frac{2}{3}$
d.
$\frac{\sqrt{2}}{3}$
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Q63 nat
An urn contains $5$ red marbles, $4$ black marbles and $3$ white marbles. Then, the number of ways in which $4$ marbles can be drawn so that at the most three of them are red is ___________.
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Q64 mcq
Let $y=y(x)$ be a solution of the differential equation, $\sqrt{1 -x^{2}} \frac{dy}{dx} +\sqrt{1 -y^{2}} = 0, |x| < 1.$ If $y(\frac{1}{2})= \frac{\sqrt{3}}{2},$ then $y(\frac{-1}{\sqrt{2}})$ is equal to
a.
$\frac{\sqrt{3}}{2}$
b.
$- \frac{1}{\sqrt{2}}$
c.
$\frac{1}{\sqrt{2}}$
d.
$- \frac{\sqrt{3}}{2}$
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Q65 mcq
The inverse function of $f(x) = \frac{8^{2}^{x}-8^{-2}^{x}}{8^{2}^{x}+8^{-2}^{x}},x\in (-1, 1),$ is __________.
a.
$\frac{1}{4}log_{e}( \frac{1+x}{1-x})$
b.
$\frac{1}{4}log_{e}( \frac{1-x}{1+x})$
c.
$\frac{1}{4}(log_{e}) log_{e}( \frac{1-x}{1+x})$
d.
$\frac{1}{4}log_{8}(\frac{1+x}{1-x})$
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Q66 mcq
Let $f :R R$ be such that for all $x\in R(2^{1+x} + 2^{1-x}), \,f(x)$ and $(3^{x} + 3^{-x})$ are in A.P., then the minimum value of $f(\vec{x})$ is
a.
$2$
b.
$3$
c.
$0$
d.
$4$
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Q67 mcq
The mean and the standard deviation (s.d.) of $10$ observations are $20$ and $2$ respectively. Each of these $10$ observations is multiplied by $p$ and then reduced by $q,$ where $p\neq 0$ and $q\neq 0.$ If the new mean and new s.d. become half of their original values, then $q$ is equal to
a.
$-5$
b.
$10$
c.
$-20$
d.
$-10$
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Q68 mcq
If $c$ is a point at which Rolle’s theorem holds for the function, $f(x) = log_{e}(\frac{x^{2}+\alpha}{7x})$ in the interval $[3, 4],$ where $\alpha \in R,$ then $f''(c)$ is equal to
a.
$-\frac{1}{12}$
b.
$\frac{1}{12}$
c.
$-\frac{1}{24}$
d.
$\frac{\sqrt{3}}{7}$
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Q69 mcq
If $\int \frac{cosxdx}{362} =f(x)(1 + sin^{6}x)\frac{1}{\lambda} +c$ , where $c$ is a constant of integration, then $\lambda f(\frac{\pi}{3})$ is equal to $sin x(1+sin x)^{3}$
a.
$-\frac{9}{8}$
b.
$2$
c.
$\frac{9}{8}$
d.
$-2$
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Q70 mcq
Let the volume of a parallelepiped whose coterminous edges are given by $\vec{u}= Λ†i+ Λ†j+\lambda Λ†k, \vec{v}= Λ†i+ Λ†j+ 3Λ†k$ and $\vec{w}= 2Λ†i+ Λ†j+ Λ†k$ be $1$ cu. unit. If $\theta$ be the angle between the edges $\vec{u}$ and $\vec{w},$ then the value of $cos\theta$ can be
a.
$\frac{7}{6\sqrt{6}}$
b.
$\frac{7}{6\sqrt{3}}$
c.
$\frac{5}{7}$
d.
$\frac{5}{3\sqrt{3}}$
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Q71 mcq
Let two points be $A(1, -1)$ and $B(0, 2).$ If a point $P(x', \,y')$ be such that the area of $\Delta PAB= 5$ sq. units and it lies on the line $3x+y-4\lambda = 0,$ then a value of $\lambda$ is
a.
$4$
b.
$3$
c.
$1$
d.
$-3$
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Q72 mcq
The shortest distance between the lines $\frac{x-3}{3} = \frac{y-8}{-1} = \frac{z-3}{1}$ and $\frac{x+3}{-3} = \frac{y+7}{2} = \frac{z-6}{4}$ is
a.
$2\sqrt{30}$
b.
$\frac{7}{2}\sqrt{30}$
c.
$3\sqrt{30}$
d.
$3$
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Q73 mcq
Let $f(x) =xcos^{-1}(-sin|x|),x\in [-\frac{\pi}{2} , \frac{\pi}{2} ],$ then which of the following is true?
a.
$f'$ is increasing in $(-\frac{\pi}{2}, 0)$ and decreasing in $(0, \frac{\pi}{2})$
b.
$f'(0) = -\frac{\pi}{2}$
c.
$f$ is not differentiable at $x= 0$
d.
$f'$ is decreasing in $(-\frac{\pi}{2} , 0)$ and increasing in $(0, \frac{\pi}{2})$
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Q74 nat
The sum $\sum ^{20}_{k=1}(1 + 2 + 3 + … +k)$ is ___________.
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Q75 mcq
For which of the following ordered pairs $(\mu ,\delta ),$ the system of linear equations $x+ 2y+ 3z= 1$ $3x+ 4y+ 5z=\mu$ $4x+ 4y+ 4z=\delta$ is inconsistent?
a.
$(4, 3)$
b.
$(4, 6)$
c.
$(1, 0)$
d.
$(3, 4)$
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