When a sound wave of frequency 300 Hz passes through a medium, the maximum displacement of a particle of the medium is 0.1 cm. The maximum velocity of the particle is equal to
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Solution
aω = 0.1 × 2π × 300 = 60 π cms-1
A crane is used to lift 1000 kg of coal from a mine 100 m deep. The time taken by the crane is 1 hour. The efficiency of the crane is 80%. If g = 10 ms-2, then the power of the crane is
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Solution
A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is \(\overrightarrow{F}\), the net force on the remaining three arms of the loop is
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Solution
The least count of a stopwatch is 0.2 second. The time of 20oscillations of a pendulum is measured to be 25 second.The percentage error in the measurement of time will be
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Solution
\(\frac{0.2}{25}\times 100=0.8\)
Work done in turning a magnet of magnetic moment M by an angle of 90º from the mgnetic meridian is n times the corresponding work done to turn through an angle of 60º,where n is
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Solution
For the same cross-sectional area and for a given load, the ratio of depressions for the beam of a square cross-section and circular cross-section is
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Solution
If Avogadro number is 6 × 1023, then number of protons,neutrons and electrons in 14 gms of 6C14 are respecitvely
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Solution
A body starts from rest and acquires a velocity V in time T.The work done on the body in time t will be proportional to
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Solution
Which of the following statements are true regarding Bohr’s model of hydrogen atom?
(I)Orbiting speed of electron decreases as it shifts to discrete orbits away from the nucleus
(II)Radii of allowed orbits of electron are proportional to the principal quantum number
(III)Frequency with which electrons or bit around the nucleus in discrete orbits is inversely proportional to the cube of principal quantum number
(IV)Binding force with which the electron is bound to the nucleus increases as it shifts to outer orbits
Select correct answer using the codes given below.Codes :
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Solution
Orbital speed varies inversely as the radius of the orbit.
\(v\alpha \frac{1}{n}\)
A rectangular coil of single turn, having area A, rotates in a uniform magnetic field B with an angular velocity ω about an axis perpendicular to the field. If initially the plane of the coil is perpendicular to the field, then the average induced emf when it has rotated through 90° is
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Solution
Initially flux, φ = BA cos θ = BA
After rotating through an angle 90°.
Flux through the coil is zero.
So, Δφ = BA
If λ = 10 Å then it corresponds to
A and B are two metals with threshold frequencies 1.8 × 1014Hz and 2.2 × 1014Hz.Two identical photons of energy 0.825 eV each are incident on them. Then photoelectrons are emitted in (Take h = 6.6 × 10–34Js)
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Solution
A light having wavelength 300 nm fall on a metal surface.The work function of metal is 2.54 eV,what is stopping potential ?
The de-Broglie wave length of a proton (mass = 1.6 × 10–27kg) accelerated through a potential difference of 1 kV is
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Solution
The temperature of the Sun is measured with
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Solution
Temperature of stars can be determined by Wein’s displacement law
λm=constant