List of top Physics Questions

A lift raises 50 passengers of average weight \(600\,\text{N}\) each to a height of \(100\,\text{m}\) in time \(T\). If average power used is \(15\,\text{kW}\), then the value of \(T\) is:
A wheel is rotating with angular speed \( \omega \). Another identical wheel with moment of inertia three times the first is initially at rest. It is suddenly coupled to the first. What fraction of the original kinetic energy is lost?
If the earth were to suddenly shrink to \( \dfrac{1}{64} \) of its present volume, keeping mass constant, then what would be the new duration of the day?
The position of a \(3\,\text{kg}\) mass moving along the \(x\)-axis is given by \(x = 0.3 \cos (\omega t)\,\text{m}\). If \(K(t)\) denotes the kinetic energy at time \(t\), then the value of \( \dfrac{K\left( \dfrac{\pi}{60} \right)}{K\left( \dfrac{\pi}{30} \right)} \) is:
The number of significant figures in quantity \( 0.00005041 \; \text{J} \) is:
A plane electromagnetic wave of wave interface 10W/m2 strikes a small mirror of area 20 cm2, held perpendicular to the approaching wave. The radiation force on the mirror will be:
Area of the cross-section of a wire is measured using a screw gauge. The pitch of the main scale is 0.5 mm. The circular scale has 100 divisions and for one full rotation of the circular scale, the main scale shifts by two divisions. The measured readings are listed below.
 
Measurement conditionMain scale readingCircular scale reading
Two arms of gauge touching each other without wire0 division4 divisions
Attempt-1: With wire4 divisions
20 divisions
Attempt-2: With wire
4 divisions
16 divisions

What are the diameter and cross-sectional area of the wire measured using the screw gauge?
 
Output of the following logic circuit is:
logic circuit
The metal which has the highest work function in the following is:
If the average power per unit area delivered by an electromagnetic wave is \( 9240 \, \text{Wm}^{-2} \), what is the amplitude of the magnetic field in the wave?
For a hydrogen atom, the energy of a stationary electron is given by \( E_n = -\frac{13.6}{n^2} \, \text{eV} \). The energy required to excite the electron to the second excited state and to the ionized state are:
Current density in a cylindrical wire of radius \( R \) varies with radial distance as \( \beta (r + r^2) \). What is the current through the shaded section (sector angle \( \pi/6 \)) of the wire as shown in the figure?
Current density in a cylindrical wire of radius R
Two positive charges of 10 \( \mu \text{C} \) and 12 \( \mu \text{C} \) are 10 cm apart. What is the work done in bringing them 6 cm closer?
A compass needle oscillates 20 times per minute at a location with dip \( 45^\circ \) and magnetic field \( B_1 \). It oscillates 30 times per minute at another location where dip is \( 30^\circ \) and field is \( B_2 \). Find the ratio \( \frac{B_1}{B_2} \).
Electrostatic force between two identical charges placed at a distance \( r \) is \( F \). A slab of width \( \frac{r}{5} \) and dielectric constant 9 is inserted between them. Then, the new force between the charges is:
A car engine has a power of 20 kW and runs for 1 hour. If the thermal efficiency is 40\% and ambient temperature is 300 K, then what is the energy generated by fuel combustion?
A bead of mass 400 g is moving along a straight line under a force delivering constant power 1.2 W. If the bead is initially at rest, the speed attained after 6 seconds is (in \( \text{ms}^{-1} \))
Two rectangular blocks of masses 40 kg and 60 kg are connected by a string on a frictionless table. A force of 1000 N is applied on the 60 kg block away from the 40 kg block. Find the tension in the string.
A car travels with a speed of 40 km/h. Rain drops fall vertically but the traces on the side window make an angle of \( 30^\circ \) with the vertical. Find the magnitude of rain’s velocity with respect to the car.
A particle of mass \(2 \times 10^{-27} \, \text{kg}\) has de-Broglie wavelength of \(3.3 \times 10^{-10} \, \text{m}\). The kinetic energy of this particle is: (Given: Planck’s constant \( h = 6.6 \times 10^{-34} \, \text{Js} \))
A plane electromagnetic wave of frequency \(50 \, \text{MHz}\) travels in free space. If the average energy densities in the electric and magnetic fields are \(K_E\) and \(K_B\), then:
The ratio of radii of 3rd and 6th Bohr’s orbits in a hydrogen atom is:
The values of \( Y \) and \( Z \) in the given logic circuit are:
values of Y and Z in the given logic circuit
The quantities that don’t change when a resistor connected to a battery is heated due to the current are:
A battery with a \(12\,\text{V}\) emf has an initial charge of \(80\,\text{A·h}\). If the potential across the terminals remains constant until it is fully discharged, how long can the battery deliver energy at a rate of \(120\,\text{W}\)?