List of top Physics Questions

A uniform solid right circular cone of base radius $r$ is joined to a uniform solid hemisphere of radius $r$ and of the same density, so as to have a common face. The centre of mass of the composite solid lies on the common face. The height of the cone is
A uniform rod of mass $m$, length $L$, area of cross-section $A$ and Young's modulus $Y$ hangs from a rigid support. Its elongation due to its own weight will be
An $RL$ circuit in which $R = 5\,\Omega$ and $L = 4\,H$ is connected to a $22\, V$ battery at $t = 0$. For this circuit at what rate the energy is being stored in the inductor when the current in circuit is $1 \,A$ ?
A disc is placed on a surface of pond which has refractive index $5/3$. A source of light is placed $4\,m$ below the surface of liquid. The minimum radius of disc needed so that light is not coming out is
At time $t = 0$, activity of radioactive substance is $1600 \,Bq$, at $t = 8 \,s$ activity falls to $100 \,Bq$. The activity at $t = 2\, s$ is
An echo repeats four syllables. The distance of the reflecting surface, if it takes one-fifth of a second to pronounce or hear one syllable distinctly is (Velocity of sound $= 340\,ms^{-1}$)
In a transistor amplifier, $\beta = 62$, $R_L = 5000\,\Omega$ and input resistance of the transistor is $500\, \Omega$. What is power amplification ?
A thin equiconvex lens of refractive index $\frac{3}{2}$ and radius of curvature $30\, cm$ is put in water (refractive index = $\frac{4}{3})$, its focal length is
A stationary object at $ 4{}^\circ C $ and weighing 3.5 kg falls from a height 2000 m on a snow mountain at $ 0{}^\circ C $ . If the temperature of the object just before hitting the snow is $ 0{}^\circ C $ and the object before comes to rest immediately $ (g=10\text{ }m/{{s}^{2}}) $ and latent heat of ice $ =3.5\times {{10}^{5}} $ J/s), then the object
A spring balance $A$ and a beam balance $B$ are used to weigh the same object at a place on the equator and a place on the pole of the earth. Then
"A spherically symmetric gravitational system of particles has a mass density $\rho =\Biggl \{ \begin{array} \ \rho_0 \ \text{for} \ r \le R\\ 0 \ \text{for} r\ > \ R \\ \end{array}$ , where $\rho _0$ is a constant. A test mass can undergo circular motion under the influence of the gravitational field of particles. Its speed v as a function of distance r from the centre of the system is represented by"
A spherical solid ball of volume $V$ is made of a material of density $\rho_1$ It is falling through a liquid of density $\rho_2(\rho_2 < \rho_1)$. Assume that the liquid applies a viscous force on the ball that is $F = krv$ where $r$ is the radius of the ball and $v$ is the speed and $k$ is the constant of proportionality. The terminal speed of the ball is
A satellite revolves round the earth. Air pressure inside the satellite is maintained at $76 \,cm$ of mercury. What will be height of mercury column in a barometer tube $100\, cm$ long placed in the satellite?
A rigid bar of mass $M$ is supported symmetrically by three wires each of length $L$. Those at each end are of copper and the middle one is of iron. The ratio of their diameters, if each is to have the same tension, is equal to
Two point charges $+2C$ and $+ 6C$ repel each other with a force of $12 \,N$. If a charge of $- 2C$ is given to each of these charges the force will now be
A box whose mass is $5\, kg$ lies on a spring balance inside a lift. The lift starts to ascend with an acceleration of $2\, ms ^{-2}$. The reading of the machine or balance is $\left(g=10\, ms ^{-2}\right)$
In intrinsic semiconductor at room temperature number of electrons and holes are
Fusion reaction is initiated with the help of
An electric motor operates on a $50\, V$ supply and a current of $12\, A$. If the efficiency of the motor is $30\%$, what is the resistance of the winding of the motor?
After $2$ hours $1 / 16$ th of initial amount of a certain radioactive isotope remains undecayed. The half-life of the isotope is :
A wheel having moment of inertia $2\,kg-m^2$ about its vertical axis, rotates at the rate of $60$ rpm about this axis. The torque which can stop the wheel's rotation in one minute would be
A transparent cube of $15\,cm$ edge contains a small air bubble. Its apparent depth when viewed through one face is $6\,cm$ and when viewed through the opposite face is $4\,cm$. Then, the refractive index of the material of the cube is
A synchronous relay satellite reflects TV signals and transmits TV programme from one part of the world to the other because its
A stone is tied to a string of length $ l $ and is whirled in a vertical circle with the other end of the string as the centre. At a certain instant of time, the stone is at its lowest position and has a speed u. The magnitude of the change in velocity as it reaches a position where the string is horizontal (g being acceleration due to gravity) is
A tank is filled with water upto height $H$. When a hole is made at a distance $h$ below the level of water, what will be the horizontal range of water jet?