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9601.

52. If speed of an object revolving in a circular path isdoubled and angular speed is reduced to half oforiginal value, then centripetal acceleration willbecome/remainSame(2) Double(3) Half(4) Quadruple

Answer»

the centripetal acceleration will become half

9602.

6.The resistance of a conductor is reduced to halfits initial value. In doing so the heating effectsin the conductor will become

Answer»

I have a doubt.H=(V^2/R)×tFrom the above formula, H=R^-1So, heating effect should be doubled.

9603.

Keeping the Potential difference constant, the resistance of a circuit is doubled. The currentwill become ?A. DoubleB. HalfC. One-fourthD. Four times

Answer»
9604.

Faraday's laws

Answer»

a law stating that when the magnetic flux linking a circuit changes, an electromotive force is induced in the circuit proportional to the rate of change of the flux linkage.

9605.

5.Under what circumstances would your weight become zero?

Answer»

Weight is given by the expression :

Weight=W=mg

so when g= acceleration due to gravity becomes zero then weight will be zero.

Conditions when weight will become zero:

1. Under a free fall

2. At the centre of the earth.[g=0]

3. In space, where zero gravity is there.

9606.

need for a standard unit

Answer»

Standardized units of measure are important because if everyone was using different measurement systems, dimensions of different objects and inventions wouldn't be converted currently from them when the inventor to other inventors or manufacturers.

9607.

8. The length of the table is 3 metre, here 3 is the(b) unit(d) quantity(a) standardc) magnitude

Answer»

In 3 metre 3 is called magnitude and metre is called as unit.

9608.

Name two fossil fuels.

Answer»
9609.

The frequency and velocity of a wave arerespectively 15 x 103 Hż and 330 m/s. Findits wave length-(1)

Answer»
9610.

heal Amagearesl at lo

Answer»
9611.

he word 'deteriorate' in the passage meansto become healthyto become strong2rto become wors4. to become heal

Answer»

The answer is to become worse

9612.

FOSSIL FUELS

Answer»

A fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms, containing energy originating in ancient photosynthesis.

9613.

Deduce an expression of escape velocity of an object from the surface of aplanet of mass 'M' and radius 'R.

Answer»
9614.

7.0 × 106 m/s and a nevelocity of 4.0 x 106 m/s?Ans. 1.5 x 10 m/s, towardsi8. A 10 g moving body is acted upon by a force of 1ofor 3 μs. Compute the impulse and the changevelocity of the body.udes 3x10-5 N s , 3 × 10-3 ins-1

Answer»
9615.

21. दे ब्रोइ तरंग से क्या समझते हैं ? इस तरंग कीड़ तरंग Tझते हैं ? किस प्रयोग से इ Tग3

Answer»

The de Broglie wavelength is the wavelength, λ, associated with a massive particle and is related to its momentum, p, through the Planck constant, hlamda=h/mv

9616.

4. The volume of a cube having sides 1.2 m isappropriately expressed as(1) 1.728 x 106 cm3(2) 1.7 x 106 cm3(3) 1.8 x 106 cm3(4) 1.73 x106 cm3

Answer»

volume of cube = (1.2x 10²)³ cm³ = (1.2)³ x 10^6 = 1.728 x 10^6 cm³

hence, option (a) is correct

volume of cube = a³ (1.2)³= 1.728m³1 m³ = 10^6 cm³volume = 1.728 × 10^6 cm³

9617.

29. एक 50 kg द्रव्यमान को उठाने में कल4900 J कार्य प्रयोग में लाया गया। दव्यमानको इस ऊँचाई तक उठाया गया :7.00

Answer»
9618.

sucking through a straw, a boy can reduce the pressure in his lungs to 750 mm of Hg(density 13.6 g/cm3), Using a straw, he can drink water from a maximum depth of(1) 13.6 cm(3) 0.136 cmBy(2) 1.36 cm(4) 10 cm

Answer»
9619.

Calculate the speed of sound in air at N.T.P. if thedensity of air at N.T.P. İs 1.29 kg/m? and γ for air is1.4

Answer»

At NTP temp = 293K and pressure is 1 atm, y= 1.4 and density is 1.29kg/m3

also P/density = RT and the value of R = 286.9J/k-kg

speed of sound in air is given by The speed of sound in air at20oC(293.15 K)and absolute pressure1 barcan be calculated as

c= (1.4 (286.9 J/K kg) (293.15 K))1/2

=343.1(m/s)

9620.

10. The wavelength of a sound wave corresponding to a frequency of(b) 17 cm(d) 17 m(a) 1.7 cm(c) 1.7 m

Answer»

d. 17m

the wavelengthrange for hearing is 0.0172 m to 17.2 m.

9621.

Class work Problems (5 Marks)56 A polythene piece rubbed with wool is found to have a negative charge of 3 x 10" C.(a) Estimate the number of electrons transferred (from which to which(b) Is there a transfer of mass from wool to polythene??)[1.875 x 10h, Yes, 1.71 x 101" kgl

Answer»

thanque

9622.

Calculate the massaf the enty ivonEbyxlon andg 9.eml

Answer»
9623.

5. Calculate the distance between twoprotons such that electrical repulsive forcebetween them is equal to the weight ofeither proton. (0.1186m)

Answer»
9624.

Two equal and like charges when placed 5 cm apan!experience a repulsive force of 0.144 newtons. Themagnitude of the charge in micro-coulomb will be(1) 0.2(2) 2(3) 20(4) 12

Answer»

answer 1 option is right

Let the charge on each object is q Given, separation between them , r = 5cm = 0.05 m force act between them , F = 0.144N [ repulsive force ]

Now, according to Coulombs law, F = Kq²/r² 0.144 = 9 × 10⁹ × q²/(0.05)² 0.016 × (0.05)² × 10⁻⁹ = q² Taking square root both sides, 0.4 × 0.05 × 10⁻⁵ = q q = 0.02 × 10⁻⁵ C = 0.2 × 10⁻⁶ C

Hence, magnitude of each charge = 0.2μC

9625.

. The minimum distance to the obstacle to hear an echo is (V is speed of sound in air)(a) V/10 m(b) V/20 m(C) V/30 m(d) V/40 m

Answer»

the reflecting object should be V/20 m from the source of sound

9626.

hat is the effect of ageing on hearing?

Answer»

It can be difficult to distinguish age-related hearing loss from hearing loss that can occur for other reasons, such as long-term exposure to noise. Noise-induced hearing loss is caused by long-term exposure to sounds that are either tooloudor last too long.

9627.

charges of 2 x 10CandThe electrostatic force on a small sphere of charge 0.4 μC du toanother small sphere of charge -0.8 uC in air is 0.2 N. (a) What isthe distance between the two spheres? (b) What is the force on the10 C P1.2

Answer»

thank you

9628.

1.is a form of energy which produces a sensation of hearing in our ears.

Answer»

Sound is a form of energy which produces a sensation of hearing in our ears.

9629.

5. Solve the following examples.a. The specd of sound in air at 0 °C is332 m/s. If it increases at the rateof 0.6 m/s per degree, what will bethe temperature when the velocityhas incrcased to 344 m/s?(Ans: 200 °C)

Answer»

The speed of sound in air at 0℃ = 332m/s

If it increases at the rate of 0.6m/s per degree,

Speed at x℃ = (332 + 0.6x)℃

Thus 344 = 332 + 0.6x344 - 332 = 0.6x12 = 0.6xx = 12/ 0.6 = 20℃

Temperature is 20℃

9630.

i)Derive an expression for critical velocityof satellite.

Answer»

Consider a satellite of mass m revolving round the Earth at a, height 'h' above the surface of the Earth.

Let M be the mass and R be the radius of the Earth.

The satellite is moving with velocity V and the radius of the circular orbit isr=R+hr=R+h. Centripetal force = Gravitational force

∴Mv2cr=GMmr2∴Mvc2r=GMmr2

∴v2c=GMr∴vc2=GMr

∴vc=√GMR+h∴vc=GMR+h

This is the expression for critical velocity of a satellite moving in a circular orbit around the Earth,

We know that,

gh=GM(R+h)2gh=GM(R+h)2

GM=gh(R+h)2GM=gh(R+h)2

Substituting in equation (1), we get

∴vc=√gh(R+h)2R+h∴vc=gh(R+h)2R+h

∴vc=√gh(R+h)∴vc=gh(R+h)

whereghghis the acceleration due to gravity at a height above the surface of the Earth.

9631.

a substance has critical angle 45° for yellow light?

Answer»

The formula relating refractive index (μ)and critical angle (C) is given by :μ=1/sinCμ=1/sin45 =√2

9632.

Define critical velocity of satellite and obtain an expression for it.

Answer»

1

2

9633.

LIIVOUUUULIतीन संधारित्रों का संयोजन चित्र में प्रदर्शित है। बिन्दुओं A तथा B के बीच सम्पूर्ण संयोजन की तुल्य धारिता15 माइक्रोफैरड है तो संधारित्र C की धारिता ज्ञात कीजिये।Combination of three capacitors has been10fshown in the figure. Equivalent capacitanceof the whole combination between thepoints A and B is 15 uF then calculate the10/capacitance of the capacitor C.

Answer»

{1/(10+10)} + { 1/C } = 1/15 C= 60

1/20+1/c=1/151/c=1/15-1/201/c=1/60c=60

c= 60 is the correct ans

60 is the correct answer

c= 60 is the right answer

60 is the right answer of the following

9634.

Three capacitors of 10 μ, 20 μ F and 50 μF are connectedin series. Find the total capacitance.MARCHIAPRIL. 2018

Answer»

wrong

9635.

Show that the critical velocity of a bodyrevolving in circular orbit very close to thesurface of a planet of radius R and mean density

Answer»

Critical Velocity (Vc)

l The minimum velocity required to revolve in a circular orbit around a planet is called critical velocity.

Vc=√[ ( G M ) / R ]

_ _ _ _ _ ( 1 )Where ,

G = Gravitational Constant

M = Mass of planet

R = Radius of planet

The density ( ρ ) of a body can be define as mass enclosed per unit volume

Therefore,

ρ = M / V

i.e.

M = ρ V

Volume of spherical planet is

V = ( 4 / 3 ) π R^3

The mass of planet can be given as

M = ρ ( 4 / 3 ) π R^3

Putting this value in equation ( 1 ) we get,

Vc=√[ ( ( 4 / 3 ) G ρ π R^3) / R ]

Vc= 2√[ ( G ρ π R^2) / 3 ]

Vc= 2R√[( Gρ π ) / 3 ]

9636.

82.The critical temperature of CO2 is-(2)55oC(4)273 K(3) 147.1°Cfived mass o

Answer»
9637.

(The escape velocity of a body from the surface of theearth is 11-2 Km/s. If a satellite were to orbit close tothe surface, what would be its critical velocity?

Answer»
9638.

More than one correct type8. At what angle should a body be projected with a velocity 24 ms-1 just to pass over the obstacle 14 m highat a distance of 24 m. [Take g = 10 ms2](A) tan 8 19/5(B) tan 8 1(C) tan θ = 3(D) tan 02

Answer»
9639.

Show that the critical velocity of a bodyrevolving in circular orbit very close to thesurface of a planet of radius R and mean densityis 2R1

Answer»

wrong hai answer

9640.

velocity of a bodyrevolving in circular orbit very close to thesurface of a planet of radius R and mean density(I) Show that the critical2 R \sqrt{\frac{\pi \sqrt{3 G}}{3}}

Answer»

Critical Velocity (Vc)

The minimum velocity required to revolve in a circular orbit around a planet is called critical velocity.

Vc=√[ ( G M ) / R ]

_ _ _ _ _ ( 1 )

Where ,

G = Gravitational Constant

M = Mass of planet

R = Radius of planet

The density ( ρ ) of a body can be define as mass enclosed per unit volume

Therefore,

ρ = M / V

i.e.

M = ρ V

Volume of spherical planet is

V = ( 4 / 3 ) π R3

The mass of planet can be given as

M = ρ ( 4 / 3 ) π R3

Putting this value in equation ( 1 ) we get,

Vc=√[ ( ( 4 / 3 ) G ρ π R3) / R ]

Vc= 2√[ ( G ρ π R2) / 3 ]

Vc= 2R√[( Gρ π ) / 3 ]

9641.

26. For hearing an echo, minimum distance of the obstaclebe(Speed offrom the source of sound must besound 344 ms )(A) 16.2 m(C) 172 m(B) 17.2 m(D) 17.2 cnm

Answer»

As the sensation of sound persists in our brain for about 0.1 s, to hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1s. Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) ×0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance. I.e., 34.4/2 = 17.2 m

9642.

Long Answer4. Define critical angle. Derive a relation between critical angle and refractive index.

Answer»

the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.

How do a critical angle and a refractive index relate?

Originally Answered: What is the relation between refractive index and critical angle?The critical angle is that angle at which, if a ray is incident while passing from a denser to a rarer medium, the angle of refraction is 90o.

⇒sinicrsin90o=1μ where,

sinicr is the critical angle, and,

μ is the refractive index for a ray passing from the rarer to the denser medium.

⇒sinicr=1μ

⇒icr=arcsin(1μ).

Let us take an example of light passing from water to air. The refractive index for light passing from air to water is 43.

⇒icr=arcsin(34)=48.59o.

9643.

valueofCritical wavelength:

Answer»

critical wavelength: The free-spacewavelengththat corresponds to thecriticalfrequency. Note: Thecritical wavelengthis equal, in meters, to the speed of light (3 × 108m/s) divided by thecriticalfrequency in hertz

critical wavelength:The free-spacewavelengththat corresponds to thecritical frequency.Note:The critical wavelength is equal, in meters, to thespeed of light(3 × 108m/s) divided by the critical frequency inhertz.

This HTML version of FS-1037C was last generated on Fri Aug 23 00:22:38 MDT 1996

90% of the area under the absorbance curve

critical wavelength:The free-spacewavelengththat corresponds to thecritical frequency.Note:The critical wavelength is equal, in meters, to thespeed of light(3 × 108m/s) divided by the critical frequency inhertz.

The wavelength at which the summed absorbance reaches 90% of total absorbance is defined as the 'critical wavelength' and is considered to be a measure of the breadth of sunscreen protection. Filters are then classified as 'broad spectrum', having a significant part of their absorbance in the UVA, when the critical wavelength is longer than 370 nm.

Thewavelengthat which the summed absorbance reaches 90% of total absorbance is defined as the 'critical wavelength' and is considered to be a measure of the breadth of sunscreen protection.

9644.

2. Find the equivalent capacitance if three capacitors each of 12 puf are connected in seriesand if they are connected in parallel.(Ans: Cs Apr, Cp = 361)

Answer»

In seriesequivalent will be= 12*12*12/12+12+12= 48uf

in parallel= 12+12+12= 36 uf

9645.

what is critical velocity

Answer»
9646.

Which one has greater critical angles- diamond or glass?

Answer»

Diamond (Because diamonds have a high index of refraction (about 2.3), the critical angle for the total internal reflection is only about 25 degrees. Incident light therefore strikes many of the internal surfaces before it strikes one less than25 degrees and then emerges.)

9647.

t1 be the time taken by a body to clear the topof a building and t2 be the time spent in air, thert2: t1 will be-4 Ift

Answer»
9648.

4. Two particles are moving in airoular paths of radir, and r wilth same angular speeds Then the ratioof their centripetal acceleration is(4)小時47. A particle P is moving in a circle of radius r with

Answer»
9649.

article is moving along a vertical circle of radiusA pR. Atassume critical condition at C)?p. what will be the velocity of particle1609

Answer»
9650.

3)DE(4For hearing an echo, the distance from the obstacle should be(1) less than 10 m(3)17 m or more(2) between 10 m and 15n(4) none of these

Answer»

As the sensation of sound persists in our brain for about 0.1 s, to hear a distinct echo the time interval between the original sound and the reflected one must be at least 0.1s. If we take the speed of sound to be 344 m/s at a given temperature, say at 22 ºC in air, sound must go to the obstacle and reach back the ear of the listener on reflection after 0.1s.Hence, the total distance covered by the sound from the point of generation to the reflecting surface and back should be at least (344 m/s) ×0.1 s = 34.4 m. Thus, for hearing distinct echoes, the minimum distance of the obstacle from the source of sound must be half of this distance. I.e., 34.4/2 = 17.2mhence 17 metres and more

For hearing distinct echoes,the minimum distance of the obstacle from the source of sound must be half of this distance that is 17.2m.