List of top Physics Questions

A Carnot engine of 50 % efficiency takes heat from a source of 400 K. To change efficiency to 70 % without changing the sink temperature, the new temperature of source should be (nearer to)
For the same angle of incidence, the angles of refraction of light ray in different media A, B, C are $35^{\circ}$, $25^{\circ}$, $15^{\circ}$. If $V_{A}, V_{B}, V_{C}$ are velocities of light in A, B, C media respectively, then
The refractive index of water is $\frac{4}{3}$ and that of glass is $\frac{3}{2}$. The refractive index of glass with respect to water is
The rms speed of oxygen molecule at some temperature is $150 \text{ ms}^{-1}$. Then the rms speed of hydrogen molecule at the same temperature is
In which of the following thermodynamic process, the internal energy of system remains constant
A blackened platinum wire of surface area $10^{-5}\text{m}^{2}$ is maintained at temperature of 3000K. At what rate the wire is loosing energy [Stefan-Boltzmann constant $\sigma=5.67\times10^{-8}\text{W m}^{-2}\text{K}^{-4}$]
Calculate the amount of work done in spraying a drop of a liquid of radius 1 mm into million identical droplets under isothermal conditions. [surface tension of liquid $=550\times10^{-3}\text{Nm}^{-1}$]
An earthen pitcher containing 9.5 kg of water loses one gram of water per minute due to evaporation. If water equivalent of pitcher is 0.5 kg. The time required to cool the water in pitcher from $30^{\circ}\text{C}$ to $28^{\circ}\text{C}$ is (Neglect radiation effect and Take latent heat of vaporization 500 cal $\text{g}^{-1}$)
A copper wire of negligible mass, length 1 m and area of cross-section $10^{-6}\text{m}^{2}$ is kept on a smooth horizontal table. One end of the wire is fixed and other end of the wire attached with a ball of mass 1 kg. If the ball and wire are rotating with 20 rad $\text{s}^{-1}$, an elongation of $10^{-3}\text{m}$ is observed in the wire, find its Young's modulus
In simple harmonic motion, at mean position
A 1200 kg artificial satellite is in an orbit of radius $2R_{E}$ about the earth. The energy required to transfer it to an orbit of radius $3R_{E}$ is ($g=10\text{ms}^{-2}$, $R_{E}=6400 \text{ km}$)
A particle starting from the origin executes simple harmonic motion along x-axis. Its velocity at any instant t is given by $v_{x}=22 \cos(\frac{\pi t}{2}) \text{ cm s}^{-1}$. The total distance covered by the particle in time $t=4.5 \text{ sec}$ is
A body of mass $5\text{ kg}$ is projected vertically upwards from a point $X$ from the ground with an initial speed of $20\text{ ms}^{-1}$. It rises to a point $Y$ where its kinetic energy is reduced to $400\text{ J}$. If the body experiences a constant air resistance of $10\text{ N}$ throughout its motion, then the vertical distance between $X$ and $Y$ is (Acceleration due to gravity $=10\text{ ms}^{-2}$)
The acceleration of a uniform disc rolling down an inclined plane of length $1.75\text{ m}$ is $1/3$ times the acceleration due to gravity. If a solid sphere is rolling down from the top of the same inclined plane, then the velocity with which it reaches the bottom of the plane is
A block is kept at the top of a rough inclined plane of length $2.8\text{ m}$ and angle of inclination $\cos^{-1}(0.6)$. If the coefficient of kinetic friction between the block and the upper half of the plane is $0.3$ and between the block and the lower half of the plane is $0.5$, then the velocity with which the block reaches the bottom of the plane is (acceleration due to gravity $=10\text{ ms}^{-2}$)
Three balls $A$, $B$ and $C$ of equal mass are moving in the same order along the same straight line on a smooth horizontal surface. Initially, ball $A$ moves towards right with a velocity of $6\text{ ms}^{-1}$, ball $B$ moves towards left with a velocity of $4\text{ ms}^{-1}$ and ball $C$ moves towards right with a velocity of $3\text{ ms}^{-1}$. If the coefficient of restitution between any two balls is $0.8$, then the relative velocity of balls $B$ and $C$ after collision is
If three particles of masses $2m$, $m$ and $4m$ are moving in three mutually perpendicular directions with velocities $3\text{ ms}^{-1}$, $4\text{ ms}^{-1}$ and $3\text{ ms}^{-1}$ respectively, then the magnitude of the velocity of the center of mass of the system of three particles is
A stone of mass $400\text{ g}$ tied to one end of a string is rotated in a horizontal circle of radius $125\text{ m}$. If the string can withstand a maximum tension of $50\pi^{2}\text{ N}$ then the minimum time period with which the stone can be rotated is
Cars $X$ and $Y$ begin the race simultaneously with velocities $8\text{ ms}^{-1}$ and $4\text{ ms}^{-1}$, moving in a straight line with uniform accelerations $2\text{ ms}^{-2}$ and $4\text{ ms}^{-2}$ respectively. If they reach final point at the same instant, then the length of the path is
A projectile is thrown into space so that it attains a maximum possible range of $200\text{ m}$. Taking the point of projection as origin, the coordinates of the point where the velocity of projectile is minimum is
$\beta=\frac{F}{v^{2}}\cos(\alpha t)$, if $F$ is force, $v$ is velocity, $t$ is time, then the dimensional formulae of $\alpha$, $\beta$ are respectively
A bike race is conducted on a circular track of radius $60\text{ m}$. If the slowest bike, weighing $120\text{ kg}$, moved around the track at a constant speed of $108\text{ kmph}$, then the time taken by it to complete one lap and its acceleration are respectively
The de Broglie wavelength of a particle of mass $m$ moving with a velocity $v$ is given by
A p-n junction diode acts as a closed switch when it is
The work function of a metal depends on