List of top Physics Questions

For ordinary terrestial experiments, the observer in an inertial frame in the following cases is

The SI unit of gravitational constant is _____

___ system of units was accepted by the scientist of the general conference on weights and measures.

A car is standing $200\, m$ behind a bus, which is also at rest. The two start moving at the same instant but with different forward accelerations. The bus has acceleration $2 \, m/s^2$ and the car has acceleration $4 \, m/s^2$. The car will catch up with the bus after a time of :

A radioactive nucleus $A$ with a half-life $T$, decays into a nucleus $B$. At $t = 0$, there is no nucleus $B$. At sometime t, the ratio of the number of $B$ to that of $A$ is $0.3$. Then, $t$ is given by :

An observer is moving with half the speed of light towards a stationary microwave source emitting waves at frequency $10\, GHz$. What is the frequency of the microwave measured by the observer ? (speed of light $= 3 \times 10^8 \, ms^{-1}$)

In an experiment a convex lens of focal length $15\, cm$ is placed coaxially on an optical bench in front of a convex mirror at a distance of $5 \,cm$ from it. It is found that an object and its image coincide, if the object is placed at a distance of $20 \,cm $ from the lens. The focal length of the convex mirror is :

The temperature of an open room of volume $30 \, m^3$ increases from $17^{\circ}C$ to $27^{\circ}C$ due to the sunshine. The atmospheric pressure in the room remains $1 \times 10^5 \, Pa$. If $n_i$ and $n_f$ are the number of molecules in the room before and after heating, then $n_f-n_i$ will be :

The moment of inertia of a uniform cylinder of length $l$ and radius $R$ about its perpendicular bisector is $l$. What is the ratio $\frac{l}{R}$ such that the moment of inertia is minimum ?

A slender uniform rod of mass $M$ and length $l$ is pivoted at one end so that it can rotate in a vertical plane (see figure). There is negligible friction at the pivot. The free end is held vertically above the pivot and then released. The angular acceleration of the rod when it makes an angle $\theta$ with the vertical is :

In a physical balance working on the principle of moments, when $5\,mg$ weight is placed on the left pan, the beam becomes horizontal. Both the empty pans of the balance are of equal mass. Which of the following statements is correct ?

A time dependent force $F = 6t$ acts on a particle of mass $1\,kg$. If the particle starts from rest, the work done by the force during the first $1\,sec$. will be :

A body of mass $m=10^{-2} \, kg$ is moving in a medium and experiences a frictional force $F=-kv^2$. Its initial speed is $v_0=10 \, ms^{-1}$. If, after $10\,s$, its energy is $\frac{1}{8} mv_0{^{2}}$, the value of $k$ will be :

A conical pendulum of length $1\,m$ makes an angle $\theta = 45^{\circ}$ w.r.t. $Z-axis$ and moves in a circle in the $XY$ plane. The radius of the circle is $0.4 \,m$ and its center is vertically below $O$. The speed of the pendulum, in its circular path, will be : (Take $g = 10 \, ms^{-2}$)

In a coil of resistance $100 \, \Omega$, a current is induced by changing the magnetic flux through it as shown in the figure. The magnitude of change in flux through the coil is :

A capacitance of $2 \, \mu F$ is required in an electrical circuit across a potential difference of $1.0\, kV$. A large number of $1 \, \mu F$ capacitors are available which can withstand a potential difference of not more than $300\, V$. The minimum number of capacitors required to achieve this is :

A uniform wire of length $l$ and radius $r$ has a resistance of $100 \, \Omega$ . It is recast into a wire of radius $\frac{r}{2}$. The resistance of new wire will be :

In the above circuit the current in each resistance is

An electron and a proton enter a magnetic field perpendicularly both have same kinetic energy. Which of the following is true?

The reason a moving coil galvanometer cannot be used with an alternating current is that

Select the output Y of the combination of gates shown in figure for inputs A = 1, B = 0; A = 1, B = 1 and A = 0, B = 0 respectively.

The temperature co-efficient of resistance of a wire is 0.00125/°C. Its resistance is 1Ω at 300 K. At what temperature, its resistance will be 2Ω?

If the vertical component of earth's magnetic field at a place is √3 times the horizontal component, then the value of dip at that place is

In Young's double slit experiment, using a monochromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is \(\lambda\) is K units. Then the intensity of light at a point where path difference is \(\frac{\lambda}{3}\) is

If the mass shown in figure is slightly displaced and then let go, then the system shall oscillate with a time period of