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A soap bubble, blown by a mechanical pump at the mouth of a tube, increases in volume, with time, at a constant rate. The graph that correctly depicts the time dependence of pressure inside the bubble is given by:

A force F acts between sodium and chlorine ions of salt (sodium chloride) when put 1 cm apart in air. The permittivity of air and dielectric constant of water are ${\epsilon }_0$ and K respectively. When a piece of salt is put in water electrical force acting between sodium and chlorine ions 1 cm apart is

The string of pendulum of length I is displaced through ${90}^{\circ }$ from the vertical and released. Then the minimum strength of the string in order to withstand the tension, as the pendulum passes through the mean position is

A battery is used to charge a parallel plate capacitor till the potential difference between the plates becomes equal to the electromotive force of the battery. The ratio of energy stored in the capacitor and work done by the battery will be?

In figure shows a man of mass 60 kg standing on a light weighing machine kept in a box of mass 30 kg. The box is hanging from a pulley fixed to the ceiling through a light rope, the other end of which is held by the man himself. If the man manages to keep the box at rest, what is the weight shown by the machine ? What force should he exert on the rope to get his correct weight on the machine ?

In a projectile motion, velocity at maximum height is

A magnet is suspended horizontally in the earth's magnetic field. When it is displaced and released, it oscillates in a horizontal plane with a period T. If a piece of wood of same moment of inertia as the magnet is attached along the length to the magnet, the new period of oscillation of the system would be -

A parallel plate capacitor with plate area A and initial separation d is connected to battery of EMF $V_0$. work done by external force to increase separation of plates from d to 2d slowly is

[Battery remains connected]

A mechanical wave needs what all to propagate?

An object is placed infront of a concave mirror of focal length f. A virtual image is formed with a magnification, the object has to moved by a distance

Estimate the proportion of boron impurity which will increase the conductivity of a pure silicon sample by a factor of $100$. Assume that each boron atom creates a hole, and the concentration of holes in pure silicon at the same temperature is $7\times {10}^{15}$ holes per cubic meter. Density of silicon is $5\times {10}^{28}$ atoms per cubic meter.

In a full wave rectifier

For a uniform square sheet from which another smaller square is cut out as shown in the figure, find out the distance of centre of mass of the remaining part from the $y-$axis. Consider the origin as shown in figure.

As shown in the figure, a triangular sheet is removed from a uniform rectangular sheet. Then, shift of the centre of mass for the new shape will be:

A boy whirls a stone in a horizontal circle of radius $1.5\text{m}$ and at height $2.0\text{m}$ above level ground. The string breaks, and the stone flies off horizontally and strikes the ground after travelling a horizontal distance of $10\text{m}$. What is the magnitude of the centripetal acceleration of the stone during the circular motion?

Distance between the trough and crest of a wave is $1.5\text{m}$ while distance between two crests is $5\text{m}$. Which of the following wavelengths is possible?

A block of weight 200 N is pulled along a rough horizontal surface at a constant speed by a force of 100 N acting at an angle of ${30}^{\circ }$ above the horizontal. The coefficient of friction between the block and the surface is

A p-n photodiode is fabricated from a semiconductor with band gap
of 2.8 eV. Can it detect a wavelength of 6000 nm?

A glass wind screen whose inclination with the vertical can be changed is mounted on a car. The car moves horizontally with a speed of 2 m/s. At what angle $\alpha$ with the vertical should the screen be placed so that the rain drops falling downwards with velocity 6 m/s strike the windscreen perpendicularly?

Distance between successive compression and rarefaction in a sound wave is $1\text{m}$. If the velocity of sound is $360{\text{ms}}^{-1}$, find the frequency of sound wave.

A block M hangs vertically at the bottom end of a uniform rope of constant mass per unit length. The top end of the rope is attached to a fixed rigid support at $O$. A transverse wave pulse (Pulse 1) of wavelength ${\lambda }_0$ is produced at point $O$ on the rope. The pulse takes time $T_{OA}$ to reach point $A$. If the wave pulse of wavelength ${\lambda }_0$ is produced at point $A$ (Pulse 2) without disturbing the position of $M$ it takes time $T_{AO}$ to reach point $O$. Which of the following options is/arc correct?

The slope of tangent to the curve $y=\sqrt{2x^2-3x+2}$ at point(s) where its ordinate is equal to abscissa, can be

In an experiment on photo electric effect, the emitter and the collector plates are placed at a separation of 10 cm and are connected through an ammeter without any cell (figure 42-E3). A magnetic field B exists parallel to the plates. The work function of the emitter is 2.39 eV and the light incident on it has wavelengths between 400 nm and 600 nm. Find the minimum value of B for which the current registered by the ammeter is zero. Neglect any effect of space charge.

A parallel plate capacitor has a uniform electric field $\overrightarrow{E}$ in the space between the plates. If the distance between the plates is $d$ and the area of each plate is $A$, the energy stored in the capacitor is [${\epsilon }_0-\text{permittivity}$ of free space]

The magnitude of vector $\overrightarrow{A},\overrightarrow{B}$ and $\overrightarrow{C}$ are respectively 12, 5 and 13 units and $\overrightarrow{A}+\overrightarrow{B}=\overrightarrow{C}$ then the angle between $\overrightarrow{A}$ and $\overrightarrow{B}$ is

The displacement of the particle at x = 0 of a stretched string carrying a wave in the positive x-direction is given by f(t) = A sin$\left(\frac{t}{T}\right)$ The wave speed is v. Write the wave equation.

If transmissivity is zero then -



$a$ is absorptive power and $r$ is reflective power.

A ball is dropped from the edge of a roof. It takes $0.1\text{s}$ to cross a window of height $2.0\text{m}$. Find the height of the roof above the top of the window.

The given figure shows the isotherms of a fixed mass of an ideal gas at three temperatures $T_A,T_B$ and $T_C$ then

A projectile is fired horizontally from an inclined plane (of inclination ${30}^{\circ }$ with the horizontal) with speed $50\text{m/s}$. If $g=10{\text{m/s}}^2$, the range measured along the incline is

Electric potential in a region is varying according to the relation $V=\frac{3x^2}{2}-\frac{y^2}{4}$ , where $x$ and $y$ are in $\text{meter}$ and $V$ is in $\text{volt}$. Electric field intensity in $\text{N/C}$ at a point $(1\text{m},2\text{m})$ is

For the given arrangement, find the value of electric field at $C$.