Assume that a drop of liquid

Question: Assume that a drop of liquid evaporates by decrease in its surface energy, so that its temperature remains unchanged. What should be the minimum radius of the drop for this to be possible? The surface tension is $T$, density of liquid is $\rho$ and $L$ is its latent heat of vaporization.$\frac{\rho \mathrm{L}}{\mathrm{T}}$$\sqrt{\frac{T}{\rho L}}$$\frac{\mathrm{T}}{\mathrm{pL}}$$\frac{2 \mathrm{~T}}{\rho \mathrm{L}}$Correct Option: , 4 Solution:...

Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4

Question: Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4 . Then the number of spectral lines in the emission spectra will be :-6235Correct Option: 1 Solution:...

A uniform cylinder of length

Question: A uniform cylinder of length $\mathrm{L}$ and mass $\mathrm{M}$ having cross- sectional area A is suspended, with its length vertical, form a fixed point by a massless spring, such that it is half submerged in a liquid of density $\sigma$ at equilibrium position. The extension $x_{0}$ of the spring when it is in equilibrium is : (Here $\mathrm{k}$ is spring constant)$\frac{\mathrm{Mg}}{\mathrm{k}}$$\frac{\mathrm{Mg}}{\mathrm{k}}\left(1-\frac{\mathrm{LA} \sigma}{\mathrm{M}}\right)$$\fra...

Solve this following

Question: Two masses $\mathrm{m}_{1}=5 \mathrm{~kg}$ and $\mathrm{m}_{2}=10 \mathrm{~kg}$, connected by an inextensible string over a frictionless pulley, are moving as shown in the figure. The coefficient of friction of horizontal surface is $0.15$. The minimum weight $m$ that should be put on top of $m_{2}$ to stop the motion is :- $27.3 \mathrm{~kg}$$43.3 \mathrm{~kg}$$10.3 \mathrm{~kg}$$18.3 \mathrm{~kg}$Correct Option: 1 Solution:...

Energy required for the electron excitation in

Question: Energy required for the electron excitation in $\mathrm{Li}^{++}$from the first to the third Bohr orbit is:(A) $108.8 \mathrm{eV}$$122.4 \mathrm{eV}$$12.1 \mathrm{eV}$$36.3 \mathrm{eV}$Correct Option: 1 Solution:...

A thin liquid film formed

Question: A thin liquid film formed between a U-shaped wire and a light slider supports a weight of $1.5 \times 10^{-2} \mathrm{~N}$ (see figure). The length of the slider is $30 \mathrm{~cm}$ and its weight negligible. The surface tension of the liquid film is :- $0.025 \mathrm{Nm}^{-1}$$0.0125 \mathrm{Nm}^{-1}$$0.1 \mathrm{Nm}^{-1}$$0.05 \mathrm{Nm}^{-1}$Correct Option: 1 Solution:...

Given in the figure are two blocks A and B of weight

Question: Given in the figure are two blocks A and B of weight $20 \mathrm{~N}$ and $100 \mathrm{~N}$, respectively. These are being pressed against a wall by a force $\mathrm{F}$ as shown. If the coefficient of friction between the blocks is $0.1$ and between block B and the wall is $0.15$, the frictional force applied by the wall on block B is :- $120 \mathrm{~N}$$150 \mathrm{~N}$$100 \mathrm{~N}$$80 \mathrm{~N}$Correct Option: 1 Solution:...

A diverging lens with magnitude of focal length 25cm is placed at a distance of

Question: A diverging lens with magnitude of focal length $25 \mathrm{~cm}$ is placed at a distance of $15 \mathrm{~cm}$ from a converging lens of magnitude of focal length $20 \mathrm{~cm}$. A beam of parallel light falls on the diverging lens. The final image formed is :real and at a distance of $40 \mathrm{~cm}$ from the divergent lensreal and at a distance of $6 \mathrm{~cm}$ from the converreal and at a distance of $40 \mathrm{~cm}$ from convergent lensvirtual and at a distance of $40 \math...

The transistion from the state

Question: The transistion from the state $\mathrm{n}=4$ to $\mathrm{n}=3$ in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from :-$4 \rightarrow 2$$5 \rightarrow 4$$2 \rightarrow 1$$3 \rightarrow 2$Correct Option: , 2 Solution:...

Question: A diverging lens with magnitude of focal length $25 \mathrm{~cm}$ is placed at a distance of $15 \mathrm{~cm}$ from a converging lens of magnitude of focal length $20 \mathrm{~cm}$. A beam of parallel light falls on the diverging lens. The final image formed is :real and at a distance of $40 \mathrm{~cm}$ from the divergent lensreal and at a distance of $6 \mathrm{~cm}$ from the converreal and at a distance of $40 \mathrm{~cm}$ from convergent lensvirtual and at a distance of $40 \math...

Solve this following

Question: A block of mass $m$ is placed on a surface with a vertical cross section given by $y=\frac{x^{3}}{6}$. If the coefficient of friction is $0.5$, the maximum height above the ground at which the block can be placed without slipping is :- $\frac{1}{3} m$$\frac{1}{2} \mathrm{~m}$$\frac{1}{6} m$$\frac{2}{3} m$Correct Option: , 3 Solution:...

A wooden cube

Question: A wooden cube (density of wood 'd') of side ' $\ell$ ' floats in a liquid of density ' $\rho$ ' with its upper and lower surfaces horizontal. If the cube is pushed slightly down and released, it performs simple harmonic motion of period ' $T$ '. Then, ' $T$ ' is equal to :-$2 \pi \sqrt{\frac{\ell \rho}{(\rho-\mathrm{d}) g}}$$2 \pi \sqrt{\frac{\ell \mathrm{d}}{\rho \mathrm{g}}}$$2 \pi \sqrt{\frac{\ell \rho}{d g}}$$2 \pi \sqrt{\frac{\ell \mathrm{d}}{(\rho-\mathrm{d}) g}}$Correct Option: ...

If a ball of steel

Question: If a ball of steel (density $\rho=7.8 \mathrm{~g} \mathrm{~cm}^{-3}$ ) attains a terminal velocity of $10 \mathrm{~cm} \mathrm{~s}^{-1}$ when falling in a tank of water (coefficient of viscosity $\eta_{\text {water }}=8.5 \times 10^{-4} \mathrm{~Pa}$.s) then its terminal velocity in glycerine ( $\rho=1.2 \mathrm{~g} \mathrm{~cm}^{-3}, \eta=13.2$ Pa.s) would be nearly :-$1.6 \times 10^{-5} \mathrm{~cm} \mathrm{~s}^{-1}$$6.25 \times 10^{-4} \mathrm{~cm} \mathrm{~s}^{-1}$$6.45 \times 10^{...

In an experiment for determination of refractive index of glass of a prism by

Question: In an experiment for determination of refractive index of glass of a prism by $\mathrm{i}-\delta$, plot, it was found that a ray incident at angle $35^{\circ}$, suffers a deviation of $40^{\circ}$ and that it emerges at angle $79^{\circ}$. In that case which of the following is closest to the maximum possible value of the refractive index?$1.8$$1.5$$1.6$$1.7$Correct Option: , 2 Solution:...

The minimum force required to start pushing a body up a rough

Question: The minimum force required to start pushing a body up a rough (frictional coefficient $\mu$ ) inclined plane is $\mathrm{F}_{1}$ while the minimum force needed to prevent it from sliding down is $\mathrm{F}_{2}$. If the inclined plane makes an angle $\theta$ from the horizontal such that $\tan \theta=2 \mu$ then the ratio $\frac{F_{1}}{F_{2}}$ is :- 4123Correct Option: , 4 Solution:...

An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20 .

Question: An observer looks at a distant tree of height $10 \mathrm{~m}$ with a telescope of magnifying power of 20 . To the observer the tree appears :20 times nearer10 times taller10 times nearer20 times tallerCorrect Option: , 3 Solution: Angular magnification is 20 ....

Two merucry drops

Question: Two merucry drops (each of radius ' $r$ ') merge to form a bigger drop. The surface energy of the bigger drop, ifs $\mathrm{T}$ is the surface tension, is :$2^{5 / 3} \pi r^{2} \mathrm{~T}$$4 \pi \mathrm{r}^{2} \mathrm{~T}$$2 \pi r^{2} T$$2^{8 / 3} \pi r^{2} \mathrm{~T}$Correct Option: , 4 Solution:...

A magnetic needle of magnetic moment

Question: A magnetic needle of magnetic moment $6.7 \times 10^{-2} \mathrm{Am}^{2}$ and moment of inertia $7.5 \times 10^{-6} \mathrm{~kg} \mathrm{~m}^{2}$ is performing simple harmonic oscillations in a magnetic field of $0.01 \mathrm{~T}$. Time taken for 10 complete oscillations is :$6.98 \mathrm{~s}$$8.76 \mathrm{~s}$$6.65 \mathrm{~s}$$8.89 \mathrm{~s}$Correct Option: , 3 Solution:...

Consider a car moving on a straight road with a speed of

Question: Consider a car moving on a straight road with a speed of $100 \mathrm{~m} / \mathrm{s}$. The distance at which car can be stopped, is : $\left[\mu_{\mathrm{k}}=0.5\right]$ $800 \mathrm{~m}$$1000 \mathrm{~m}$$100 \mathrm{~m}$$400 \mathrm{~m}$Correct Option: , 2 Solution:...

Work done in increasing

Question: Work done in increasing the size of a soap bubble from a radius of $3 \mathrm{~cm}$ to $5 \mathrm{~cm}$ is nearly (Surface tension of soap solution $=0.03 \mathrm{Nm}^{-1}$ ) :-$2 \pi \mathrm{mJ}$$0.4 \pi \mathrm{mJ}$$4 \pi \mathrm{mJ}$$0.2 \pi \mathrm{mJ}$Correct Option: , 2 Solution:...

Monochromatic light is incident on a glass prism of angle A.

Question: Monochromatic light is incident on a glass prism of angle A. If the refractive index of the material of the prism is $\mu$, a ray, incident at an angle $\theta$, on the face $A B$ would get transmitted through the face $\mathrm{AC}$ of the prism provided : $\theta\cos ^{-1}\left[\mu \sin \left(\mathrm{A}+\sin ^{-1}\left(\frac{1}{\mu}\right)\right)\right]$$\theta\cos ^{-1}\left[\mu \sin \left(\mathrm{A}+\sin ^{-1}\left(\frac{1}{\mu}\right)\right)\right]$$\theta\sin ^{-1}\left[\mu \sin \...

Hysteresis loops for two magnetic materials

Question: Hysteresis loops for two magnetic materials $\mathrm{A}$ and $\mathrm{B}$ are given below : These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to useB for electromagnets and transformers.A for electric generators and transformers.A for electromagnets and B for electric transformers.A for transformers and $B$ for electric generators.Correct Option: 1 Solution: For electromagnet and transformers, we require the cor...

Water is flowing continuously

Question: Water is flowing continuously from a tap having an internal diameter $8 \times 10^{-3} \mathrm{~m}$. The water velocity as it leaves the tap is $0.4 \mathrm{~ms}^{-1}$. The diameter of the water stream at a distance $2 \times 10^{-1} \mathrm{~m}$ below the tap is close to :-$9.6 \times 10^{-3} \mathrm{~m}$$3.6 \times 10^{-3} \mathrm{~m}$$5.0 \times 10^{-3} \mathrm{~m}$$7.5 \times 10^{-3} \mathrm{~m}$Correct Option: , 2 Solution:...

The upper half of an inclined plane with inclination

Question: The upper half of an inclined plane with inclination $\phi$ is perfectly smooth, while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom, if the coefficient of friction for the lower half is given by- $2 \sin \phi$$2 \cos \phi$$2 \tan \phi$$\tan \phi$Correct Option: , 3 Solution:...

A green light is incident from the water to the air - water interface at the critical angle

Question: A green light is incident from the water to the air - water interface at the critical angle $(\theta)$. Select the correct statement.The spectrum of visible light whose frequency is more than that of green light will come out to the air medium.The entire spectrum of visible light will come out of the water at various angles to the normalThe entire spectrum of visible light will come out of the water at an angle of $90^{\circ}$ to the normal.The spectrum of visible light whose frequency...