Physics Test 12...

Three charges e, e and - 2e are placed at the corners of the triangle as shown. The net dipole moment of the system is

A mass is attached to one end of a spring of spring constant k. The spring is stretched and then released such that its amplitude of oscillation is A. For a displacement y from the mean position, if the kinetic energy is 44% of its potential energy, then y in terms of A is

At a given instant there are 25% of undecayed radioactive nuclei in a sample. After 20s, the number of undecayed nuclei reduces to 12.5%. The extra time required in which the number of undecayed nuclei will further reduce to 3.125% of the sample is-

The escape velocity for an atmospheric particle 2000 km above the earth's surface is (Radius of the earth = 6.4 x 10⁶ m and g = 10 m s^{- 2} )

A circular disc of radius r and thickness r/6 has moment of inertia I about an axis passing through its centre and perpendicular to its plane. It is melted and recasted to a solid sphere. The moment of inertia of the sphere about its diameter as axis of rotation is

When an UV light of 10¹⁵ Hz and intensity 2 W/m² is directed at a metal surface, photoelectrons emitted were found to have a maximum kinetic energy of 1.6 eV. If the work functions for different materials are as follows: Potassium 2.2 eV, Sodium 2.3 eV, Lithium 2.5 eV and Calcium 3.2 eV, identify the metal in the given problem.

Two sources of sound S₁ and S₂ each emitting waves of wavelength A are kept symmetrically on either side of the centre 0 of a circle ABCD such that S₁O = S₂O = K . When the detector is moved along the circumference of the circle, the number of maxima recorded by the detector in one revolution is

A boat capable of a speed v in still water wants to cross a river of width d. The speed of the water current increases linearly from zero at either bank to a maximum of u at the middle of the river. When the boat is rowed at right angles to the bank, its downstream drift is

Figure shows the plot of a potential energy function of a conservative system U versus x. Which of the following statements is correct ?

A sphere with some cavity has outer radius R. It rolls down an inclined plane without slipping and attains a speed v at the bottom. When this sphere slides down without rolling on the frictionless inclined plane of same height its speed at the bottom is 5v/4. The radius of gyration of the sphere is