A body of density''is dropped slowly on the surface of a lake of depth .If the density of the lake water be' then the time taken by the body to reach the bottom of the lake is ‘

Official solved question paper for West Bengal Joint Entrance Examination. Review all 80 questions, official answer keys, and detailed step-by-step solutions below, or attempt online with timer and negative marking.
A body of density''is dropped slowly on the surface of a lake of depth .If the density of the lake water be' then the time taken by the body to reach the bottom of the lake is ‘
Beyond what distance,the ray optics is sufficiently valid when the aperture is 6 mm wide and the wavelength is ?
50 m
40 m
60 m
10 m
A plano-convex lens fits exactly into a plano-concave lens.Their plane surfaces are parallel to each other.If lenses are made of different materials of refractive indices and and is the radius of curvature of the curved surface of the lenses,then the focal length of the combination is
Consider a fuse wire of length and radius .The time of heating for passing the maximum current will depend on
Density and volume of a body are given as and respectively. The absolute error in measurement of mass is
20 gm
30 gm
45 gm
60 gm
If a vector is rotated in the plane by an angle with respect to -axis in the clockwise direction,then for an observer at axis the vector will be
A circular coil, carrying current, has radius . The distance from the centre of the coil on the axis where the magnetic induction will be th of its value at the centre of the coil is
A square of side lies in the plane,where the magnetic field is given by where is constant.The magnetic flux passing through the square is
A resistor of resistance''draws power''when connected to an AC source.If an inductance is now placed in series with ,such that the impedance of the circuit becomes'',the power drawn will be
A simple pendulum of length has a bob of mass ,with a charge .On it a vertical sheet of charge, with surface charge density''passes through the point of suspension.At equilibrium,if the string makes an angle with the vertical,then
The equation of a transverse wave is .If the maximum particle velocity be four times that of wave velocity then
A uniform but time varying magnetic field is present in a circular region of radius ' '. The magnetic field is perpendicular and into the plane of loop and the magnitude of field is increasing at a constant rate . There is a straight conducting rod of length 2 R placed as shown in figure. The magnitude of induced emf across the rod is

From a tower of height ,a particle is thrown vertically upwards with a speed .The time taken by the particle to hit the ground is times that taken by it to reach the highest point of its path.The relation between and is
There is a ring of radius having linear charge density and rotating with a uniform angular velocity . The magnitude of the magnetic field produced by this ring at its own centre would be ( permeability of air)
Three vectors and are such that and along with .Then,the value of will be
27
-26
-68 problem is wrong.
-34
Two identical metal bars are heated in two different temperatures and allowed to cool in the same surroundings. Which one of the following figures correctly shows their cooling curves?




The inputs to a digital circuit are as shown below. The output Y is

The velocity of a particle at time is given by , where and are constants. The dimension of and are, respectively
A body initially at rest and sliding along a frictionless track from a height''(as shown in figure) just completes a vertical circle of diameter .The height''is equal to

The I-V characteristics graph shown below is exhibited by

LED
Zener diode
Photodiode
Solar cell
A person has a minimum distance of distinct vision of 50 cm .The power of lenses required to read a book at a distance of 25 cm is
3 D
1 D
2D
5 D
Three blocks of masses and are placed on a horizontal frictionless surface and a force of 30 N pulls the system as shown below.The value of tension will be

Which one of the following graphs represents the velocity-time graph of a small spherical body falling in a viscous liquid?
A ray of light travelling in air is incident on one face of a parallel glass slab of thickness and refractive index at an angle of incidence .Total time spent by the ray inside the slab is
Radiation of wavelength is incident on a photocell.The fastest emitted electron has speed . If the wavelength is changed to ,then the speed of the fastest emitted electron will be
Two spherical soap bubbles of radii and in vaccum coalesce under isothermal condition.The newly formed bubble has a radius( )given by
A radioactive element emits two -particles,one electron and two positrons.The transformed nucleus is represented by .The value of is
The magnetic moment of an iron bar is . It is now bent in such a way that it forms an arc section of a circle subtending an angle of at the centre. The magnetic moment of the arc section is
A uniform is suspended from a point ,at a variable distance ,from ,as shown in figure. To make the rod horizontal,a mass''is suspended from its end .Which set of variables will give a straight line when they are plotted?
A pipe is connected with other pipes and as shown in the figure.The areas of cross-section of and are respectively and .If the velocities of flow of water through and are and ,respectively,then velocity of flow, along is

A particle of mass is suspended from a point O by a string of length .It is given a velocity at the bottom.The difference in tension at point and at the point is 
The de-Broglie wavelength of an electron in 4th orbit is (where radius of the 1st orbit)
An electromagnetic wave,whose wave normal makes an angle of with the vertical,is travelling in air and strikes a horizontal liquid surface.While travelling through the liquid,it gets deviated by .If the speed of electromagnetic wave in air is ,then the speed of electromagnetic wave in the liquid will be
The circuit has two oppositely connected ideal diodes in parallel as shown in the figure.What is the current flowing in the circuit?

2 moles of an ideal gas with are mixed with 3 moles of another ideal gas with .The value of for the mixture is
Which of the velocity-time graph(s) can possibly represent one-dimensional motion of a particle?
The moment of inertia of a thin disc about axes are and respectively,as shown in figure.If the moment of inertia about an axis passing through the centre and perpendicular to the plane of the disc is I then,

The displacement current flows through a capacitor when the voltage across its plates
Two points of monochromatic and coherent sources of light of wavelength each, are placed as shown in figure. The initial phase difference between the sources is zero, . Mark the correct statement(s).

For Boolean variables and .Then,which of the following statements is / are correct?
The major products U and V in the following reaction are 




Among and , the species having the linear structures are
In the following sequence of reactions, what is the end product ' '?





A compound when treated with solution yields a brown precipitate.On adding hypo solution the precipitate turns white.The compound is
Three engines and C take steam at and reject it at and respectively.The most efficient engine will be
A
B
C
All the three engines will be equally efficient
In a conductance experiment, aqueous solution is added to aqueous KCl solution gradually and simultaneously the molar conductivity ( ) is measured. The correct plot of versus volume of solution is




Indicate the major product of the following reaction:





The van't Hoff Factor (i) for a dilute aqueous solution of is
Which of the following is the structure of pyrosulphuric acid?




Peroxide ion is
Paramagnetic
Ferromagnetic
Diamagnetic
Antiferromagnetic
How many isomers can a compound with molecular formula have?
2
3
4
5
Which one of the following cations gives a chocolate brown precipitate upon addition of aqueous solution of ?
A compound contains two types of atoms and .Its crystal structure is a cubic lattice with'' atoms at the corner of the unit cells and''atoms at the body centres.The simplest formula of the compound will be
The plot of radial probability density( )against for an electron in orbital of a many electron atom is given below.

The value of is
2
3
4
5
A buffer solution contains 100 ml of and 200 ml of of water is added subsequently to the buffer solution.The pH before and after dilution are [given, ]
The correct order of conductivity of separate aqueous solutions of ; (ii); (iii) and (iv) each containing octahedral complex species is
(i) < (ii) < (iii) < (iv)
(i) < (ii) < (iv) < (iii)
(i) (iv) (iii) (ii)
(iii) (iv) (ii) (i)
Borazole is prepared by heating the product isolated by reacting
boron with dinitrogen.
diborane with ammonium nitrate.
diborane with ammonia.
boron with ammonia.
The increasing order of basicity of the following compounds is

I III II
III I II
II I III
II III I
The products and in the following reaction sequence are





The van der Waal's equation : is valid for
1 mole of an ideal gas.
2 moles of a real gas.
mole of an ideal gas.
mole of a real gas.
Which one of the following does not lose water even in conc. ?

1
2
3
4
The major product in the following reaction is





Rank the following anions in order of decreasing nucleophilicity in a polar protic solvent (most → least nucleophilic).

In which of the following species, hybridisation is not associated?
For the reaction ,variation of concentration is plotted against time as shown below.

Which of the following statements is true?
Region(1)indicates equilibrium
Region(2)indicates equilibrium
Region(3)indicates equilibrium
Both the Regions(2)and(3)indicate equilibrium
In a first order reaction,the concentration of reactant decreases from 400 moles lit to 50 moles lit in .The rate constant of the reaction is(approximately)
In the following reaction sequence, the product Y is



The mass of an electron is .If its K .E.is ,its wavelength is(approximately)
250 nm
400 nm
990 nm
850 nm
The calculated magnetic moment for low spin is
2.73 BM
1.73 BM
3.23 BM
0.00 BM
Glucose is added to 1 litre of water to such an extent that equals to .The weight of glucose added is
180 gm
18 gm
1.8 gm
0.18 gm
A solution of liberates 1.27 g of iodine from an acidified KI solution. The percentage strength of is close to
An organic compound undergoes first order decomposition.The time taken for its decomposition to th and th of its initial concentration are and respectively.The value of is [Given ]
0.9
0.6
0.3
0.5
For the metal complex ,coordination number,oxidation number,number of -electrons and number of unpaired -electrons are respectively
To carry out the above conversion X and Y are respectively

1-Chloro-2-nitro-4-methylbenzene
1-Chloro-4-methyl-2-nitrobenzene
2-Chloro-1-nitro-5-methylbenzene
-Nitro-p-chlorotoluene
Which of the following statement(s) is/are correct about the given compound?

1 mole of an ideal gas undergoes the following processes:
Process Isothermal expansion at 400 K from volume to volume ,such that
Process Adiabatic expansion from volume to volume ,such that
Consider the following statements and select the correct one/s.
Which of the following statement(s)is/are correct?
Which of the following have tetrahedral structures?
Which of the following plot(s) is/are correct representation(s) of Boyle's Law?