Recent questions tagged 2003

According to Newton's law of cooling, the rate of cooling of a body is proportional to $(\Delta \theta)^n$, where $\Delta \theta$ is the difference of the temperature of the body and the surroundings, and $n$ is equal to :

asked Dec 11, 2018 by pady_1

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To get three images of a single object, one should have two plane mirrors at an angle of :

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The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by :

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The image formed by an objective of a compound microscope is :

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A 220 V, 1000 W bulb is connected across a 110 V mains supply. The power conumed will be :

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Three charges $-q_1,\;+q_2$ and $-q_3$ are placed as shown in the figure. The x-component of the force on $-q_1$ is proportional to :

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To demonstrate the phenomenon of interference we require two sourcces which emit radiations of :

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A rocket with a lift-off mass $3.5 \times 10^4 kg$ is blasted upwards with an initial acceleration of $10 m/s^2$. Then the initial thrust of the blast is :

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A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time t is proportional to :

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If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of $Li^{2+}$ is

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In the middle of the depletion layer of reverse biased p-n junction, the :

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The wavelengths involved in the spectrum of deuterium $(_1^2D)$ are slightly different from that of hydrogen spectrum, because :

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Which of the following atoms has the lowest ionization potential ?

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In the nuclear fusion reaction, $_1^2H +_1^3H \to _2^4He+n$ given that the repulsive potential energy between the two nuclei is $7.7 \times 10^{-14} J$, the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann's constant $k = 1.38 \times 10^{-23} J/K$] :

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A body executes simple harmonic motion.The potential energy (PE), the kinetic energy (KE) and total energy (TE) are measured as function of displacement $x$. Which of the following statement is true ?

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A tuning fork of known frequency 256 Hz makes 5 beats/s with the vibrating string of a piano. The beat frequency decreases to 2 beats/s when the tension in the piano string is slightly increased. The frequency of the piano string before increaseing the tension was :

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A metal wire of linear mass density of 9.8 g/m is streched with a tension of 10 kg-wt between two rigid supports 1 m apart. The wire passes at its middle point between the poles of a permanent magnet and it vibrates in resonance when carrying an alternating current of frequency n. The frequency n of the alternating source is :

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A spring of spring constant $5 \times 10^3 N/m$ is stretched initially by 5 cm from the unstreched position. Then the work required to stretch it further by another 5 cm is

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A Carnot engine takes $3 \times 10^6$ cal of heat from a reservoir at $627^{\circ}C$ and gives it to a sink at $27^{\circ}C$. The work done by the engine is :

asked Dec 11, 2018 by pady_1

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Which of the following parameters does not characterise the thermodynatic state of matter ?

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During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio $C_P/C_V$ for the gas is :

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The co-ordinates of a moving particle at any time $t$ are given by $x = \alpha t^3$ and $y = \beta t^3$. The speed of the particle at time $t$ is given by :

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The work done in placing a charge of $8 \times 10^{-18} C$ on a condenser of capacity $100 \mu F$ is :

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A thin spherical conducting shell of radius $R$ has a charge $q$. Another charge $Q$ is placed at the centre of the shell. The electrostatic potential at a point $P$ at a distance $R/2$ from the centre of the shell is :

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The displacement of a particle varies according to the relation $x=4 (\cos \pi t + \sin \pi t)$. The amplitude of the particle is :

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A sheet of aluminium foil of negligible thickness is introduced between the plates of a capacitor. The capacitance of the capacitor :

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A 3V battery with negligible internal resistance is connected in a circuit as shown in the figure. The current I, in the circuit will be :

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Which of the following cannot be emitted by radioactive substances during their decay ?

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Two identical, photocathodes recieve light of frequencies $f_1$ and $f_2$. If the velocities of the photoelectrons (of mass m) coming out are respecitvely $\nu_1$ and $\nu_2$, then :

asked Dec 11, 2018 by pady_1

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A nucleus with Z = 92 emits the following in a sequence : $\alpha, \; \alpha, \; \beta^-, \; \beta^-,\; \alpha,\; \alpha,\; \alpha, \; \alpha; \; \beta^-,\; \beta^-,\; \alpha,\; \beta^+, \; \beta^+, \; \alpha$. The $Z$ of the resulting nucleus is :

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A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 minutes, the rate is 1250 disintegrations per minute. Then, the decay constant (per minute) is :

asked Dec 11, 2018 by pady_1

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Let $\overrightarrow{F}$ be the force acting on a particle having position vector $\overrightarrow{r}$ and $\overrightarrow{\tau}$ be the torque of this force about the origin. Then :

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The core of any transformer is laminated so as to :

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In an oscillating LC circuit the maximum charge on the capacitaor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is :

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When the current changes from +2A to -2A in 0.05 s, an emf of 8 V is induced in a coil. The coefficient of self-induction of the coil is :

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The displacement y of a wave travelling in the $x$-direction is given by $y = 10^{-4} \sin (600 t - 2x + \frac{x}{3})$ metre, where, $x$ is epressed in metres and $t$ in seconds. The speed of the wave-motion, in $ms^{-1}$ is :

asked Dec 11, 2018 by pady_1

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The length of a simple pendulum executing simple harmonic motion is increase by 21%. The percentage increase in the time period of the pendulum of increased length is :

asked Dec 11, 2018 by pady_1

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Two particles A and B of equal masses are suspended from two massless springs of spring constants $k_1$ and $k_2$, respctively. If the maximum velocities, during oscillations are equal, the ratio of amplitudes of A and B is

asked Dec 11, 2018 by pady_1

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"Heat cannot be itself from a body at lower temperature to a body at higher temperature" is a statement or consequence of :

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A mass M is suspended from a spring of negligible mass. The spring is pulled a little and then released so that the mass executes SHM of time period T. If the mass is increased by $m$, the time period becomes $5T/3$, then the ratio of $\frac{m}{M}$ is :

asked Dec 11, 2018 by pady_1

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The escape velocity for a body projected vertically upwards from the surface of earth is $11\; km/s$. If the body is projected at an angle of $45^{\circ}$ with the vertical, the escape velocity will be :

asked Dec 11, 2018 by pady_1

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A wire suspended vertically from one of its ends is stretched by attaching a weight of 200 N to the lower end. The weight stretches the wire by 1 mm. Then the elastic energy stored in the wire is :

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A light spring balance hangs from the hook of the other light spring balance and a block of mass M kg hangs from the former one. Then the true statement about the scale reading is :

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A block of mass M is pulled along a horizontal frictionless surface by a rope of mass m. If a force P is applied at the free end of the rope, the force exerted by the rope on the block is :

asked Dec 11, 2018 by pady_1

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Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon

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Consider the following two statements : A. Linear momentum of a system of particles is zero. B. Kinetic energy of a system of particle is zero. Then :

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A marble block of mass 2 kg lying on ice when given a velocity of 6 m/s is stopped by friction in 10 s. Then the coefficient of friction is :

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A horizontal force of 10 N is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is 0.2. The weight of the block is :

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If the electric flux entering and leaving an enclosed surface respectively is $\phi_1$ and $\phi_2$, the electric charge inside the surface will be :

asked Dec 11, 2018 by pady_1

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Three forces start acting simultaneously on a particle moving with velocity $\overrightarrow{v}$. These forces are represented in magnitude and direcction by the three sides of a triangle ABC (as shown). The particle will now move with velocity :

asked Dec 11, 2018 by pady_1

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