Ionisation energy of He+ is 19.6×10-18J atom-1. The energy of the first stationary state (n = 1) of Li2+ is

The frequency of light emitted for the transition n = 4 to n = 2 of He+ is equal to the transition in H atom corresponding to which of the following

Based on the equation ΔE = -2.0×10-18 J (1/n2 2– 1/n12) the wavelength of the light that must be absorbed to excite hydrogen electron from level n = 1 to level n= 2 will be (h = 6.625×10-34 Js, C = 3×108 ms-1)

The bond dissociation energy of B–F in BF3 is 646 kJ mol-1 whereas that of C–F in CF4 is 515 kJ mol–1. The correct reason for higher B–F bond dissociation energy as compared to that of C–F is

Using MO theory, predict which of the following species has the shortest bond length?

The hybridisation of orbitals of N atom in NO3–, NO2+, NH4+ are respectively:

The structure of IF7 is :

If Z is the compressibility factor, van der Waals’ equation at low pressure can be written as :

The relationship among most probable velocity, average velocity and root mean

Square velocity is respectively :

A block P of mass m is placed on a horizontal frictionless plane. The second block of the same mass m is placed on it and is connected to a spring of spring constant k. The two blocks are pulled by a distance A. Block Q oscillates without slipping. What is the maximum value of the frictional force between the two bloc

Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These are being pressed against a wall by a force F as shown. If the coefficient of friction between the blocks is 0.1 and between block B and the wall is 0.15, the frictional force applied by the wall on block B is

A time-dependent force F = 6t acts on a particle of mass 1 kg. If the particle starts from rest, the work done by the force during the first 1 sec. will be :

.A spring of force constant k is cut into two pieces such that one piece is double the length of the other. Then the long piece will have a force constant of

Two blocks of masses 10 kg and 4 kg are con­nected by a spring of negligible mass and placed on a frictionless horizontal surface. An impulse gives a velocity of 14 m/s to the heavier block in the direction of the lighter block. The velocity of the centre of mass is

Two particles A and B, initially at rest, move to­wards each other under the mutual force of attraction. At the instant when the speed of A is v and the speed of B is 2v, the speed of the centre of mass of the system is

Two-point masses of 0.3kg and 0.7kg are fixed at the ends of a rod which is of length 1.4m and of negligible mass. The rod is set rotating about an axis perpendicular to its length with a uniform angular speed. The point on the rod through which the axis should pass in order that the work required for rotation of the rod is minimum is located at a distance of

A child is standing with folded hands at the centre of a platform rotating about its central axis. The kinetic energy of the system is K. The child now stretches his arms so that the moment of inertia of the system doubles. The kinetic energy of the system now is

The mass of a spaceship is 1000 kg. It is to be launched from the earth’s surface out into free space. The value of ‘g’ and ‘R’ (radius of the earth) is 10 m/s2 and 6400 km respectively. The required energy for this work will be

The height at which the acceleration due to gravity becomes g/9 (where g = the acceleration due to gravity on the surface of the earth) in terms of R, the radius of the earth, is

In a college of 300 students, every student reads 5 newspapers and every newspaper is read by 60 students. The number of newspapers is ________

If f (x) = cos (log x), then find the value of f (x) * f (4) − [1 / 2] * [f (x / 4) + f (4x)].

Given z = (1 + i√3)100, then find the value of Re (z) / Im (z).

If α, β, γ are the cube roots of p (p < 0), then for any x, y and z, find the value of [xα + yβ + zγ] / [xβ + yγ + zα].

The total number of positive integral solution for x, y, z such that x* y * z = 24, is ________.

If the letters of the word SACHIN are arranged in all possible ways, and these words are written in a dictionary, at what serial number does the word SACHIN appear?

If the pth term of an A.P. be q and qth term is p, then its rth term will be __________.

If mth terms of the series 63 + 65 + 67 + 69 + . . . . . . . . . and 3 + 10 + 17 + 24 + . . . . . . be equal, then what is the value of m?

If cos-1 p + cos−1 q + cos−1 r = π then p2 + q2 + r2 + 2pqr = ________.

The number of real solutions of tan−1 √[x (x + 1)] + sin−1 [√x2 + x + 1] = π / 2 is ___________.