Answers posted by priyanka.clay6

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Body A of mass 4m moving with speed u collides with another body B of mass 2m, at rest. The collision is head on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is :

answered Mar 6, 2020

Let $m_1$ be mass of $A$ and $m_2 $ mass of $B$ $\qquad u_1 = u \qquad \qquad u_2 = 0$$\qquad \large...

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A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the cylinder to keep the block stationary when the cylinder is vertical and rotating about its axis, will be :$(g = 10\frac{m}{s^2})$

answered Mar 6, 2020

https://clay6.com/mpaimg/1832_a.jpgNormal force acting on the block is equal to the centripetal forc...

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The correct Boolean operation represented by the circuit diagram drawn is

answered Mar 6, 2020

The given logic circuit bulb will glow when voltage across LED is high.https://clay6.com/mpaimg/183...

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The total energy of an electron in an atom in an orbit is -3.4 eV. Its kinetic and potential energies are, respectively :

answered Mar 6, 2020

In Bohr's model Kinetic energy = |Total energy | = $\frac{1}{2}$ |Potential energy| - PE & KE ha...

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Increase in temperature of a gas filled in a container would lead to :

answered Mar 6, 2020

Increase in temperature will increase kinetic energy of gas. Since $\qquad U = {\large\frac{f}{2}} n...

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In which of the following processes, heat is neither absorbed nor released by a system ?

answered Mar 6, 2020

In Adiabatic process, there is no exchange of heat.

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The Boolean Expression $(p \wedge \sim q) \vee q \vee(\sim p \wedge q)$ is equivalent to :

answered Feb 27, 2020

Solution : $(p \wedge \sim q) \vee q \vee (\sim p \wedge q)$https://clay6.com/mpaimg/1828_a.jpg http...

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A man is walking towards a vertical pillar in a straight path, at a uniform speed. At a certain point A on the path, he observes that the angle of elevation of the top of the pillar is $30^{\circ}$. After walking for 10 minutes from A in the same direction, at a point B, he observes that the angle of elevation of the top of the pillar is $60^{\circ}$. Then the time taken (in minutes) by him, from B to reach the pillar, is :

answered Feb 27, 2020

https://clay6.com/mpaimg/1827_a.jpgLet $CD = x$$\qquad BC=y$$\qquad AB =h$$\tan 30^{\circ} = \large\...

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When the light of frequency $2v_o$ (where $v_0$ is threshold frequency), is incident on a metal plate, the maximum velocity of electrons emitted is $v_1$. When the frequency of the incident radiation is increased to $5v_0$, the maximum velocity of eletrons emitted from the same plate is $v_2$. The ratio of $v_1$ to $v_2$ is

answered Feb 27, 2020

By photoelectric equation$E = W_ o+ \frac{1}{2} mv^2 \qquad [W_o = h \nu_o]$$h(2 \nu_o) = h \nu_o + ...

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The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is

answered Feb 27, 2020

For an electron in Bhor orbit$KE = -[\text{Total energy}]$$\therefore \;\;KE : \text{Total energy }$...

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For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is

answered Feb 27, 2020

Half life $T_{1/2} = 10\; minutes $$N_o = 600$After disintegration for 450 nuclei$\qquad N = 600 - 4...

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An electron of mass m with an initial velocity $\overrightarrow{V} = V_0 \hat{i} (V_0 > 0) $ enters an electric field $\overrightarrow{E} = -E_0 \hat{i} (E_0 = constant > 0)$ at $t = 0$. If $\lambda_0$ is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is :

answered Feb 27, 2020

We know$ma=eE_o$$\therefore $ Acceleration $a =\large\frac{eE_o}{m}$$V=V_o+at$$V = V_o + \large\frac...

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A small sphere of radius 'r' falls from rest in a viscous liquid. As a result, heat is produced due to viscous force. The rate of production of heat when the sphere attains its terminal velocity, is proportional to

answered Feb 27, 2020

Power = Rate of production of energy$\qquad $ = Rate of production of heat$Power = Force \times Velo...

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The power radiated by a black body is P and it radiates maximum energy at wavelength, $\lambda_0$. If the temperature of the black body is now changed so that it radiates maximum energy at wavelength $\frac{3}{4} \lambda_D$, the power radiated by it becomes nP. The value of n is

answered Feb 27, 2020

By Wien's law$\lambda_{max }\; T=constant$$\lambda_{max_1}\;T_1=\lambda_{max_2}\;T_2$$\qquad \lambda...

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A sample of 0.1 g of water at $100^oC$ and normal pressure ($1.013 \times 10^5 Nm^{-2}$) requires 54 cal of heat energy to convert to steam at $100^oC$. If the volumn of the steam produced is 167.1 cc, the change in internal energy of the sample, is

answered Feb 27, 2020

By Thermodynamic law$\Delta Q = \Delta U + \Delta W \qquad$$ [\because \Delta Q = 54 \; calories \\ ...

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Two wires are made of the same material and have the same volume. The first wire has cross-sectional area A and the second wire has cross-sectional area 3A. If the length of the first wire is increased by $\Delta x$ on applying a force F, how much forcce is needed to stretch the second wire by the same amount ?

answered Feb 27, 2020

Let $Y$ be Youngs modulus of wire$Y = \large\frac{F/A}{\Delta L/L}$$\Delta L = \large\frac{FL}{AY}$W...

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A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes a vertical circle of diameter AB = D. The height h is equal to

answered Feb 27, 2020

Since there is no friction acting total mechanical energy is conserved.$KE_{Before} + PE_{Before}= K...

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A moving block having mass m, collides with another stationary block having mass 4m. The lighter block comes to rest after collision. When the initial velocity of the lighter block is v, then the value of coefficient of restitution (e) will be

answered Feb 27, 2020

According to conservation of momentum $m_1v_1 + m_2v_2 = m_1v_1'+m_2v'_2$$m_1 = m \qquad m_2 = 4m$$...

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Three objects, A : (a solid sphere), B : (a thin circular disk) and C : (a circular ring), each have the same mass M and radius R. They all spin with the same angular speed $\omega$ about their own symmetry axes. The amounts of work (W) required to bring them to rest, would satisfy the relation

answered Feb 27, 2020

Work done in bring to rest a spinning body$\Delta W = $ change in kinetic energy $\Delta K$$\Delta W...

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Which one of the following statements is incorrect ?

answered Feb 27, 2020

Co efficient of sliding friction has no dimension $\mu_s = \large\frac{f}{N}$where $N$ is normal fo...

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A student measured the diameter of a small steel ball using a screw gauge of least count 0.001 cm. The main scale reading is 5 mm and zero of circular scale division coincides with 25 divisions above the reference level. If screw gauge has a zero error of -0.004 cm, the correct diameter of the ball is

answered Feb 27, 2020

Least count $= 0.001\; cm$$MSR = 5\;m = 0.5\;cm$$CSR = 25\; divisions$$Zero \;error = -0.004\;cm$$Di...

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The moment of the force, $\overrightarrow{F} = 4 \hat{i} + 5 \hat{j} - 6 \hat{k}$ at (2, 0, -3) about the point (2, -2, -2), is given by

answered Feb 27, 2020

Moment of force $\overrightarrow{F}=4 \hat{i}+5\hat{j} -6\hat{k}$$\qquad \qquad \qquad\qquad = d\ove...

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A block of mass m is placed on a smooth inclined wedge ABC of inclination $\theta$ as shown in the figure. The wedge is given as acceleration 'a' towards the right. The relation between a and $\theta$ for the block to remain stationary on the wedge is

answered Feb 27, 2020

https://clay6.com/mpaimg/1826_a.jpg $ma$ is the pseudo force acting on block.Resolving the forces in...

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A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform electric field $\overrightarrow{E}$. Due to the force q $\overrightarrow{E}$, its velocity increases from 0 to 6 m/s in one second duration. At that instant the direction of the field is reversed. The car continues to move for two more seconds under the influence of this field. The average velocity and the average speed of the toy car between 0 to 3 seconds are respectively

answered Feb 27, 2020

Acceleration $= \large\frac{v-u}{t} = \frac{6-0}{1}$$\qquad \qquad \;\;\;= 6\; m/s^2$$\therefore $ D...

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If the mass of the Sun were ten times smaller and the universal gravitational constant were ten times larger in magnitude, which of the following is not correct ?

answered Feb 27, 2020

$F= \large\frac{GMm}{r^2}$If $G$ becomes 10 times $F$ becomes larger.Also $g = \large\frac{GN}{r^2}$...

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A solid sphere is rotating freely about its symmetry axis in free space. The radius of the sphere is increased keeping its mass same. Which of the following physical quantities would remain constant for the sphere?

answered Feb 27, 2020

Since there is no external torque$\qquad T_{ex}=0$$\therefore \;\;\; \large\frac{dL}{dt}=0$$\implies...

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A solid sphere is in rolling motion. In rolling motion a body possesses translational kinetic energy $(K_t)$ as well as rotational kinetic energy $(K_r)$ simultaneously. The ratio $K_t : (K_t + K_r)$ for the sphere is :

answered Feb 27, 2020

Translational $KE, \qquad K_t= \frac{1}{2} mv^2$Rotational $KE \qquad \;\;\;K_r = \frac{1}{2}Iw^2$$\...

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The kinetic energies of a planet in an elliptical orbit about the Sun, at position A, B and C are $K_A, K_B$ aand $K_C$, respectively. AC is the major axis and SB is perpendicular to AC at the position of the Sun S as shown in the figure. Then

answered Feb 27, 2020

Velocity at $A$ (perihelion) is greater than veloicty at $C$ (aphelion)$\qquad V_A > V_B > V_C...

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An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is

answered Feb 27, 2020

Electrostatic force $=qE =eE$Acceleration $=a$$\therefore ma = eE$$\qquad a = \large\frac{eE}{m}$Now...

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The electrostatic force between the metal plates of an isolated parallel plate capacitor C having a charge Q and area A, is

answered Feb 27, 2020

The electrostatic force between the metal plates of an isolated parallel plate capacitor $C$ having ...

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A pendulum is hung from the roof of a sufficiently high building and is moving freely to and fro like a simple harmonic oscillator. The acceleration of the bob of the pendulum is $20 \; m/s^2$ at a distance of 5 m from the mean position. The time period of oscillation is :

answered Feb 27, 2020

Acceleration $a = w^2 x$$\qquad 20 = w^2(5)$$\qquad w^2 = 4$$\implies w = 2 \;rad/s$Time period $T =...

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A tuning fork is used to produce resonance in glass tube. The length of the air column in this tube can be adjusted by a variable piston. At room temperture of $27^oC$ two successive resonances are produced at 20 cm and 73 cm of column length. If the frequency of the tuning fork is 320 Hz, the velocity of sound in air at $27^oC$ is

answered Feb 27, 2020

Frequency $\nu = 320\;Hz$Length of resonance column for two successive resonance is $20\;cm$ and $73...

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An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of

answered Feb 27, 2020

The angular magnification of telescope $\qquad m = \large\frac{f_o}{f_e}$ andAngular resolution $= \...

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In Young's double slit experiment the separation d between the slit is 2mm, the wavelength $\lambda$ of the light used is $5896 \; A^o$ and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is $0.20^o$. To increase the fringe angular width to $0.21^o$ ( with same $\lambda$ and D ) the separation between the slits needs to be changed to

answered Feb 26, 2020

Angular width $\theta = \large\frac{\lambda}{d}$$\qquad 0.20^{\circ} = \large\frac{\lambda}{2\;mm} -...

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Unpolarised light is incident from air on a plane surface of a material of refractive index $\mu$. At a particular angle of incidence 'i', it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?

answered Feb 26, 2020

When reflected and refracted rays are perpendicular to each other.By Brewster's law$\qquad \tan i = ...

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In the combination of the following gates the output Y can be written in terms of inputs A and B as

answered Feb 26, 2020

The given gate can be written as https://clay6.com/mpaimg/1825_a.jpg

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In a p-n junction diode, change in temperature due to heating

answered Feb 26, 2020

In a $p-n$ junction change in temperature affects the overall $V-I$ characteristics of $p-n$ diode...

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In the circuit shown in the figure, the input voltage $V_i$ is 20 V, $V_{BE}$ = 0 and $V_{CE}$ = 0. The value of $I_B, \; I_C$ and $\beta$ are given by

answered Feb 26, 2020

Input voltage $\;\;V_i = 20 \;V$$ V_B = 0$$ I_C = \large\frac{V_C}{R_C}$$\qquad = \large\frac{20-0}{...

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The refractive index of the material of a prism is $\sqrt{2}$ and the angle of the prism is $30^o$. One of the two refracting surfaces of the prism is made a mirror inwards, by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflecting from the silvered surface) if its angle of incidence on the prism is

answered Feb 26, 2020

https://clay6.com/mpaimg/1824_a.jpg $\qquad \mu = \sqrt{2}$Angle of prison $A = 30^{\circ}$Since the...

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The magnetic potential energy stored in a certain inductor is 25 mJ, when the current in the inductor is 60 mA. This inductor is of inductance

answered Feb 26, 2020

Energy stored in an inductor $\qquad \qquad U = \frac{1}{2} LI^2$$25 \times 10^{-3} = \frac{1}{2} \t...

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An em wave id propagating in a medium with a velocity $\overrightarrow{V} = V \hat{i}$. The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along

answered Feb 26, 2020

For electromagnetic wave$\overrightarrow{E} \times \overrightarrow{B} = \overrightarrow{V}$$\overrig...

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An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be :

answered Feb 26, 2020

Focal length of concave mirror $f = -15$$\qquad u = -40$$\qquad \large\frac{1}{f} = \frac{1}{v_1} + ...

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An inductor 20 mH, a capacitor $100 \; \mu F$ and a resistor $50 \Omega$ are connected in series across a source of emf, $V = 10 \sin 314 \;t$. The power loss in the circuit is

answered Feb 26, 2020

Impedence $Z$ of $LC R$ series circuit $Z\;\; = \sqrt{R^2 + (\omega L - \large\frac{1}{\omega c})^2}...

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A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from

answered Feb 26, 2020

Energy of current source will be converted into potential energy of rod.

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A metallic rod of mass per unit length $0.5 \; kg \; m^{-1}$ is lying horizontally on a smooth inclined plane which makes an angle of $30^o$ with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction 0.25 T is acting on it in the vertical direction. The current flowing in the rod to keep it stationary is

answered Feb 26, 2020

https://clay6.com/mpaimg/1823_a.jpgMagnetic field $B$ acting in vertical direction$\qquad B = 0.25 ...

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Current sensitivity of a moving coil galvanometer is 5 div/mA and its voltage sensitivity (angular deflection per unit voltage applied ) is 20 div/V. The resistance of the galvanometer is

answered Feb 26, 2020

Current sensitivity of a moving cost galvanometer $\qquad I_S = \large\frac{NBA}{C} ---(1)$Voltage s...

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A set of 'n' equal resistors, of value 'R' each, are connected in series to a battery of emf 'E' and internal resistance 'R'. The current drawn is I. Now, the 'n' resistors are connected in parallel to the same battery. Then the current drawn from battery becomes 10 I. The value of 'n' is :

answered Feb 26, 2020

When $'n'$ resisters of $R\; \Omega$ each are connected in series, internal resistance $'R'$, emf $E...

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A carbon resistor of $(47 \pm 4.7) \; k \Omega$ is to be marked with rings of different colours for its identification. The colour code sequence will be :

answered Feb 26, 2020

$(47 \pm 4.7) k \Omega=47 \times 10^3 \pm 10\%$$\therefore $ colour code = yellow - violet - orange ...

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A battery consists of a variable number 'n' of identical cells ( having internal resistance 'r' each ) which are connected in series. The terminals of the battery are short- circuited and the current I is measured. Which of the graphs shows the correct relationship between I and n ?

answered Feb 26, 2020

When terminals of the battery are short circuited the measured current$\qquad I = \large\frac{\text...

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The volume (V) of a monatomic gas varies with its temperature (T), as shown in the graph. The ratio of work done by the gas, to the heat absorbed by it, when it undergoes a change from state A to state B, is

answered Feb 26, 2020

The given process is isobaric $\therefore \;\;dQ = \eta C_p dT$$\qquad \;\;\;\; = \eta ({\large\frac...

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