List of top Physics Questions

A source of sound of frequency $660\text{ Hz}$ and an observer are moving towards each other with speeds of $31\text{ kmph}$ and $23\text{ kmph}$ respectively. If the wind blows with a speed of $5\text{ kmph}$ from observer towards the source, then the frequency of the sound heard by the observer is: (Speed of sound in air $=340\text{ ms}^{-1}$)

Water of mass \(3\text{ kg}\) in a kettle of mass \(1\text{ kg}\) at an initial temperature of \(30^\circ C\) is heated by a heater of power \(2\text{ kW}\). When the lid is open, heat is lost at a constant rate of \(250\text{ Js}^{-1}\). If specific heat capacity of kettle material is half that of water, then time required to raise temperature to \(80^\circ C\) is

The energy required to transfer a satellite of mass \(m\) from an orbit of height \(0.5R\) from the surface of the earth to an orbit of height \(2R\) from the surface of the earth is (where \(g\) is acceleration due to gravity and \(R\) is radius of earth)

Two spherical black bodies A and B of equal radii are at temperatures \(2T\) and \(3T\). If surrounding temperature is \(T\), then ratio of radiant powers emitted by A and B is

Water flows through a horizontal pipe AB of non-uniform cross section. Water enters at A of area \(4cm^2\) with pressure \(10^5Nm^{-2}\) and velocity \(20ms^{-1}\). It leaves at B of area \(8cm^2\). The pressure at B is

A wire of length \(100\text{ cm}\) is made of a material of Young’s modulus \(1.6\times10^{11}\text{ Nm}^{-2}\). If work done in stretching this wire by \(0.1\text{ cm}\) is \(2\text{ J}\), then the area of cross-section of the wire (in \(10^{-5}\text{ m}^2\)) is

If a capillary tube of inner radius \(0.5mm\) is immersed vertically in water, then mass of water risen in capillary tube is (Surface tension \(=0.07Nm^{-1}\), \(g=10ms^{-2}\))

For a particle executing simple harmonic motion, if the velocities at distances \(6\text{ cm}\) and \(8\text{ cm}\) from mean position are \(16\pi\text{ cms}^{-1}\) and \(12\pi\text{ cms}^{-1}\) respectively, then maximum acceleration is

A solid sphere rolls down without slipping on an inclined plane of angle \(30^\circ\). If angle increases to \(45^\circ\), percentage increase in acceleration is nearly

A body P of mass \(1.5\text{ kg}\) moving with velocity \(10\text{ ms}^{-1}\) makes a one dimensional elastic collision with another body Q at rest. If ratio of velocities after collision is \(1:3\), then velocity of centre of mass is

A block slides down a \(30^\circ\) inclined plane. Coefficient of friction on upper half is \[ \mu_1=\frac{1}{2\sqrt3} \] and on lower half is \[ \mu_2=\frac{1}{4\sqrt3} \] Find ratio of velocities at midpoint and bottom.

The power \(P\) (in watt) acting on a body of mass \(2\text{ kg}\) is given by \[ 4.5P=8t^2+14t+9 \] where \(t\) is time in second. If the body starts from rest at \(t=0\), then the velocity of the body at time \(t=3\text{ s}\) is

A bomb of mass \(m\) at rest explodes into three parts. If these three parts move horizontally with equal speeds in different directions, then the masses of the three parts can be

The unification of electromagnetism and optics is based on the discovery that

If minimum velocity of a projectile is \(15\text{ ms}^{-1}\) and maximum height reached is \(20\text{ m}\), then velocity of projection is (\(g=10\text{ ms}^{-2}\))

If \(B\) is magnetic induction, \(e\) is charge of electron, \(m\) is mass and \(c\) is speed of light in vacuum, then the physical quantity having dimensions of \[ \frac{4\pi mc}{Be} \] is

A body is thrown vertically upwards from earth with velocity \(60\text{ ms}^{-1}\). The ratio of displacements during first, second and third seconds is (\(g=10\text{ ms}^{-2}\))

In hydrogen atom, electron is present in $n_x$ state. The energy of Lyman spectral line of hydrogen spectrum originated from $n_x$ state is $1.635 \times 10^{-18}\text{ J}$. What is the approximate energy (in J) required to excite this electron from $n_x$ state to $(n_x+1)$ state?}

In H atom, electron is present in $n_x$ state. The angular momentum of this electron is $1.051 \times 10^{-34}\text{ Js}$. What is the energy (in J) required to excite this electron from $n_x$ state to $(n_x+1)$ state? ($h = 6.6 \times 10^{-34}\text{ Js}$; $\pi = 3.14$)}

If the length of a linear antenna is increased by $60%$ and the wavelength of the signal is decreased by $20%$, then the percentage increase in the effective power radiated by the antenna is:

If A, B and C represent the power gain, base resistance and collector resistance respectively of a transistor connected in common emitter configuration, then the common emitter current amplification factor is:

The electron and hole concentrations in a semiconductor are $5 \times 10^{18}\text{ m}^{-3}$ and $8 \times 10^{19}\text{ m}^{-3}$ respectively. If the mobilities of the electron and hole are $0.24\text{ m}^2\text{V}^{-1}\text{s}^{-1}$ and $0.01\text{ m}^2\text{V}^{-1}\text{s}^{-1}$ respectively, then the conductivity of the semiconductor is:}

If the wavelength of a spectral line in the Balmer series of hydrogen spectrum is $\frac{7.2}{R}$, then the ratio of the radii of the higher and lower orbits between which the transition of electron takes place is ($R$ - Rydberg constant):}

A thin conducting wire of length $L$ carrying a current of $2\text{ A}$ is bent into a square loop of $2$ turns and another thin conducting wire of length $2L$ carrying a current of $3\text{ A}$ is bent into a circular loop of $3$ turns. If the magnetic moment of the circular loop is $\frac{4}{\pi}\text{ A}\cdot\text{m}^2$, then the magnetic moment of the square loop is:}

When photons of wavelength $4000\text{ \AA}$ are incident on a photosensitive material of cut-off wavelength $4800\text{ \AA}$, the stopping potential is $V$. If the same photons are incident on another photosensitive material of cut-off wavelength $6000\text{ \AA}$, then the stopping potential is:}