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551.

The maximum force of static friction which comes into play before a body juststarts to slide is called(a) static friction(c) sliding friction(b) limiting friction(d) kinetic friction

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limiting friction

The maximum friction that can be generated between two static surfaces in contact with each other. Once a force applied to the two surfaces exceeds the limiting friction, motion will occur. For two dry surfaces, the limiting friction is a product of the normal reaction force and the coefficient of limiting friction

552.

B.Fill in the blanks with the correct wordsroughness, less, resistance, more1. Sliding friction tends to be....2. Friction depends on the3. Friction produces .than rolling friction.Sprinkling of fine powder on the carrom board5. Sliding friction is4.than the static friction.

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1. More 2. Roughness 3. Resistance 4. Decreases 5. Less

553.

Is static friction is a self adjusting force?

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Yeah , static friction is a self adjusting force because it comes into play when the body is lying over the surface of another body without any motion. (The body is at rest). ... It is known as self adjusting force because neither it has fixed magnitude nor direction.It adjusts according to the applied force.

554.

Time (sec)300Displacement (meter)(b) 3 m/s(a) to m/sof 3 m/s30. The - lot of(d)

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option a is the correct answer of the given 6

555.

KINEMATICsTARGET NEETparticle in returning to the starting13)and seturne toHiarting point with a speed vis fired vertically from the ground. B1032The velocity ofa particle mning with conetanm/s ater 30 sec the futine from the Intant of fing the rocket will antainthe maximum hetight 7-10 m/ss The velocity at 3 second before to is1) 30s(2)4540. A body is projected33 A stne iw dropped into a wel in which the levelof water is eow the top of the well vis veocityof sound, the time T after which the splash is Theardis gium byafter t second. The time aher which the bodypasses through the same point daring the neturnupwards with a speed u from 41. A body is released froen the sop of the tower o14)35. A stone fals fromn a baloon that is descending atmetres from groundstone from the point of release afer 10 sec is(1) 490 ma 610 mAmetres from ground(2) 510 m(4) 725 m36. Astreisdeppedfrornaheromhe groundoh,At뿍 metres from the grandanother stone is thrown up from the ground whichreaches a height 4h. The two stones will cross eachother after tnemetres from the ground42. A body dropped from the top of the yower coversa distance 7x in the last second of its yourmay, wherex is the distance covered in first seccnd. How much37. A train accelerates from rest at a constant rate afor distance x, and tme t After that is retardstime does it take to reach the grond?comes to the rest. Whrich of the following relstion 43. A body is falling from heightis correctakes t, timeto reach the ground. The time taken to cover hfirst half of height is313(4) of these

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please post clearly. Its very difficult to get your question.

556.

Q75. Static friction is necessary in case of rolling bodies. But friction is a dissipative force. How can wejustify the use of law of conservation of mechanical energy?

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557.

14. If a body having initial velocity zero is moving with uniform acceleration 8m/sec, the distance travelledby it in fifth second will be(A) 36 metres (B) 40 metres(C) 100 metres(D Zero

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. S(n th) = u +a/2(2n-1). S(5 th) = 0 + 8/2(2*5 - 1) = 4(10-1) = 4*9 = 36m

558.

A body is released from the top of a tower of height hmetres. It takes T seconds to reach the ground. Theball at the timę T/2 second is?3.12

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how a =10

559.

5. A projectile has a maximum range of 16 km. At theighest point of its motion, it explodes into two equalmasses. One mass drops vertically downwards. Thehorizontal distance covered by the other mass from thetime of explosion is:a) 8 km (b) 16 km (c) 24 km(d) 32 km6. A body of mass m is projected horizontally with avelocity v form the top of a tower of height h and itreaches the ground at a distance x from the foot of thetower. If a second body of mass 2m is projectedhorizontally form the top of a tower of height 2h, itreaches the ground at a distance 2x from the foot thetower. The horizontal velocity of the second body is:a)v (b) 2v(c) V2 v (d) v/297, A ball rolls off the top of a staircase with a horizontalvelocity u m/s. If the steps are h metre high and bmetre wide, the ball will hit the edge of the nth step, if:(a)n=2m2hu2gb2b2

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please specify one question

560.

(a) A cricket ball of 60 g. moves with aspeed of 50 metres per second. Explainwhy one cannot observe a de Brogliewave of the cricket ball.3

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The de Broglie wavelength varies inversly with the mass of a particle. So if we consider the mass of an electron and mass of a cricket ball we will see that cricket ball has the most significant mass than an electron. So we can observe the de Broglie wavelength of electron whereas the de Broglie wavelength of cricket ball is unobservable.

561.

Using theory of drift velocity, express Ohm's law.

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562.

3.2)Using second law of motion derive F=ma

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Newton’s second law of motion states that: the net external force applied on an object is directly proportional to the rate of change of linear momentum of the object.

Let the external force be F, initial velocity be u ,final velocity be v, the time interval be t.

=> p1(initial momentum ) = mu

p2(final momentum )= mv

Therefore, (rate of change of momentum)

Δp=(mv-mu)/t

According to newton’s IInd law , F α Δp

=>F =k * (mv-mu)/t { k is a constant }

In S.I.Units, the value of k is 1

So. F= m(v-u)/t

=> F = ma

Hence proved

563.

(P + a/V2) (V - b) = RTP is pressure, V is volume and T istemperature.[P] = [F/A] = [MLT -2/L2] = [ML-1T-21[V] = [L 3]

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564.

Dra w the direction of the cそrrent in the box.conductormagnetic field linescurrent

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565.

Two cubical blocks identical in dimensions float inwater in such a way that 1st block floats with halfpart immersed in water and second block floats with3/4 of its volume inside the water. The ratio of densitiesof blocks is(2) 3:4

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Take equal volume of A and B, say V.Weight of A = Weight of V/2 volume of water.Similarly, weight of B = Weight of 3V/4 volume of water.As density is weight per unit volume, the required ratio will beD(A)/D(B)=(V/2)/(3V/4) =3/4Thus, density of A : density of B = 2:3

566.

2. Arrange four basic forces in the increasing order.

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GravitationalForce– Weakestforce; but infinite range. ( Not partofstandard model)

Weak NuclearForce– Next weakest; but short range.

ElectromagneticForce– Stronger, with infinite range.

Strong NuclearForce– Strongest; but short range.

567.

State some important characteristics of magnetic line of forces duecarrying current.to a straigl

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No two magnetic lines of force intersect each other.

The field lines emerge from North Pole and merge at the South Pole.

The direction of field lines is from its south pole to its north pole.

Magnetic field lines are the closed curves.

568.

Two particles of mass 200 g each are placed at aseparation of 10 cm. Assume that the only forcesacting on them are due to their gravitationalattraction. Find the acceleration of each when theyare allowed to move

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569.

7. एक वर्ग के दो विपरीत कोनों पर आवेश Q रखे हैं। दूसरे दोविपरीत कोनों पर आवेश q रखे हैं। यदि किसी Q पर नेट वैद्युतबल शून्य हो तो Q/q बराबर है :(a) -1/2 (b) -22 (c) -1 (d) 1.

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570.

A particle moving with uniform retardationcovers distances 18 m, 14 m and 10 m insuccessive seconds, It comes to rest aftertravelling a further distance of1) 50 m 2) 8 m 3 12 m 4) 42 m

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571.

34) Too bulbs have Îłating loovd , 22 Otvo Hi, Gow and 22000voltswhich one has thegreatey nesistance

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(1) P1=100 WV1 = 220 V

P = V×IP = V × (V/R)P = V^2/R

100 = (220×220)/R1R1 = 484 ohm

(2) P2 = 60 WV2= 220 V

60 = (220×220)/R2R2 = 806.6 ohm

Hence R2 is greater than R1

572.

k!!ba pie leh 뺘 ot lable h ple-lely Δ.LI址.1

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573.

Tuco tamps, onu taled how a doov and hu thar Gowot ao ose conmeced iw posxodldl dechic suppluh. totaQampsonanaatt tor one OLd

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We have given two lamps in such a way : Power of 1st lamp, P₁ = 40W , voltage of 1st lamp, V₁ = 220V power of 2nd lamp , P₂ = 60W , voltage of 2nd lamp ,V₂ = 220V

we know, one things , Power = V²/R [ when potential difference is same then consider P = V²/R ] R = V²/P so, resistance of 1st lamp , R₁ = V₁²/P₁ = (220)²/60 = 4840/6 = 2420/3Ωresistance of 2nd lamp , R₂ = V₂²/P₂ = (220)²/40 = 48400/40 = 1210Ω

energy consumed by lamps in one hour = Energy consumed by 1st lamps in one hour + energy consumed by 2nd lamps in one hour = P₁ × 1hour + P₂ × 1 hour =(P₁ + P₂) × 1 hour = (60W + 40W) × 1 hour = 100 Wh = 100/1000 KWh [ ∵ 1 KWh = 10²Wh ]= 0.1 KWh

574.

Q.8) Write a brief note on Allotropy with suitable example.

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It is a property by which an element can exist in different forms having different physical properties or we can say existence of two or more different physical forms of a chemical element.The different physical forms in which an element can exist are known as allotropes of that element.There are three allotropes for carbon:i)Fullerene ii)Diamond iii)Carbon

575.

The time taken by a block of wood(initially at rest) to slide down a smoothinclined plane 9.8 m long (angle ofinclination is 30) is(A)see (B) 2 sec (C)4 sec (D) 1 sec

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576.

Two lamps, one rated 100:220V and the otfier 60W:220V are connected in parallelto electric supply.Find the current drawn by two bulbs frera the line,if the supplyvoltage is 220V

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Power = P = 100 WVoltage = V = 220vResistance = R

P = V²/R100 = 220×220/RR = 220× 220/100 = 484Ω==========================Power = P = 60 WVoltage = V = 220vResistance = R

P = V²/R60 = 220× 220/RR = 220× 220/60 = 806.7ΩAs the resistors are connected in parallel ,total resistance = 1/R

1/R = 1/484 + 1/806.7 = 806.7 + 484/484×806.7 = 1290.7/390442.8R =390442.8/1290.7 = 302.5 ohms Total resistance= 302.5Ω

I = current

V = IR220 = I× 302.5

I = 220/302.5 = 0.73 A

The current drawn is 0.73 A

577.

(b) Two lamps, one rated 100 W; 220 V, and the other 60 W; 220 V, are connected inparallel to electric mains supply. Find the current drawn by two bulbs from the line,if the supply voltage is 220V

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Resistance of 1st lamp, R1 = V1²/P1 = (220)²/100= 484 ohm

Resistance of 2nd lamp, R2 = V2²/P2 = (220)²/60= 806.6 ohm

Lamps are connected in parallel combination, Req = R1R2/(R1 + R2)= 484 × 806.6/(484 + 806.6)= 390394.4/1290.6= 302.5 ohm

so, I = V/Req = 220/(302.5)=.72 Amp

578.

()how how would you join three Jesistors, each of resistance 9 Ω so that theequivalent resistance of the combination is (i) 13.5 Ω, (ii) 6 Ω ?ORWrite Joule's law of heating.Two lamps, one rated 100 W; 220 V, and the other 60 W; 220 V, are connectedin parallel to electric mains supply. Find the current drawn by two bulbs fromthe line, if the supply voltage is 220 V.(a)(b)

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a.Joule's law of heating states that the heat produced in a wire is directly proportional to the product of sqaure of current flowing through it and the resistance offered by it.b. for the first bulb, P1=100W, V=220VI1V=100or, I=100/220= 0.45Afor 2nd bulb,P2=60W, V=220VI2=60or, I2=60/220=0.27A

579.

3012. Two lamps, one rated 100 W at 220 V and the other 200 W at 220V are connected-(i) in series and(ii) in parallel to electric main supply of 220V. Find the current drawn in each case.

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Resistance of 1st lamp, R1 = V1²/P1 = (220)²/100= 484 ohm resistance of 2nd lamp, R2 = V2²/P2 = (220)²/200= 242 ohm.

if lamps are connected in series , Req = R1 + R2 = 484 + 242 = 726 ohmso, I = V/Req = 220/726 = 20/66 Amp = 10/33 = 0.3 amp

if lamps are connected in parallel combination, Req = R1R2/(R1 + R2)= 484 × 242/(484 + 242)= 484 × 242/726= 44 × 242/66 = 4 × 242/6 = 484/3 ohm

so, I = V/Req = 220/(484/3) = 660/484 = 60/44 = 15/11 = 1.36 Amp

in series it is rated 0.3 ampere and in parallel it is rated 1.36 ampere

580.

lelens.Drawtheraydiagraminsupportof your answer12 Two lamps, one rated 100 W at 220 V and the other 200 W at 220V are connected ) inelectric main supply of 220V. Find the current drawn in each case.series and (ii) in parallel to3

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When in seriescurrent will be same , Voltage will be different

Power = P = 100 WVoltage = V = 220vResistance = R

P = V²/R100 = 220×220/RR = 220× 220/100 = 484Ω

Power = P = 60 WVoltage = V = 220vResistance = R

P = V²/R60 = 220× 220/RR = 220× 220/60 = 806.7Ω

As the resistors are connected in parallel ,total resistance = 1/R

1/R = 1/484 + 1/806.7 = 806.7 + 484/484×806.7 = 1290.7/390442.8R =390442.8/1290.7 = 302.5 ohms Total resistance= 302.5Ω

I = current

V = IR220 = I× 302.5

I = 220/302.5 = 0.73 A

The current drawn is 0.73 A

581.

Two lamps, one ratein parallel to electric mains supply. Find thethe line, if the supply voltage is 220 v.d 100 W: 220 V, and the other 60 W; 220 V. are connectedcurrent drawn by two bulbs from

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Power = P = 100 WVoltage = V = 220vResistance = R

P = V²/R100 = 220×220/RR = 220× 220/100 = 484Ω==========================Power = P = 60 WVoltage = V = 220vResistance = R

P = V²/R60 = 220× 220/RR = 220× 220/60 = 806.7Ω=========================As the resistors are connected in parallel ,total resistance = 1/R

1/R = 1/484 + 1/806.7 = 806.7 + 484/484×806.7 = 1290.7/390442.8R =390442.8/1290.7 = 302.5 ohms Total resistance= 302.5Ω

I = current

V = IR220 = I× 302.5

I = 220/302.5 = 0.73 A

The current drawn is 0.73 A

582.

2 lamps are connected in parallel of 40 W 220 V and other of resistance 606 ohm 60W and 220V across 220V terminal . Find total current

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583.

Example 2. The length, breadth and height ofmare 5 m, 4 m and 3 m respectively. Find thewhite washing the walls of the room and theig at the rate oft7.50 per m^2

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584.

ero.10. Suppose a is a vector of magnitude 4:5 unit due north.What is the vector (a) 3 a, (b) – 4ā?

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585.

7. Suppose the second charge in the previous problem is-1-0 x 10 C. Locate the position where a third chargewill not experience a net force.

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586.

A curent ouannnily tong

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587.

122i and ane unit veetars aslong a and y as respectvely. What is the megnstudeA 2i.tong the directiens or i-j and i j? TYou may une graptucal method

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magnitude of i+j and i-j are equal having value= √1²+1² = √2

so, direction of both vectors are i+j/√2 and i-j/√2

now component of 2i+3j in the direction of i+j/√2 and i-j/√2 are ,

(2i+3j)•(i+j)/√2 = (2+3)/√2 = 5/√2 (2i+3j(i-j)/√2 = (2-3)/√2 = -1/√2

588.

23) A 1.2 cm long pin is placedof focal length 12 cm ,at a distance of 8 cm from it. The location of image4) 10 cmperpendicular to the principle axis of a convex4.8 cm2) 12 cm3) 6 em

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Thank you

589.

the focal length of a convex mirror น/hose raditFind12 emof carvature ismirror produces three times masnuiñiod

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Radius is = 2f or f is = R/2 so given radius is 32 cm and focal length will be 32/2 = 12cm hence lens is convex lens it's focal length is +ve

Radius of curvature R = 32 cmR =2ff=R/2f=32/2f=16 cm

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590.

An object 5 em in length is held 25 em away from a converging lens of focal length10 cm. Draw the ray diagram and find the position. size and the nature of theimage formed.

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591.

5. A convex lens of focal length 25 cm and a concave lens of focal length 10 em are placed in closecontact with each other. Calculate the lens power of this combination.

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592.

(e) A convex lens of focal length 25 em and a concave lens offocallength10care placed in close contact with each other. Calculate the lens power of thicombination.All Indi

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593.

object is placed at 36 em in front of concavemirror of focal length 24 cm. Find the distance ofimage formed.

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594.

A 10 cn, tall oltect is placed perpendicular to the principal nis of aconvex lens of focal length 12 em. The distance of the object from the lens18 em. Pind the nature, position and sine of the image formed

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CONVEX LENS

Lens formula is 1/f = 1/v - 1/u

given that f=12 cm , u= -18 cm , v=?

Applying the formula we get:

1/12=1/v - (-1/18)=> 1/v=1/12+(-1/18)=>1/v=1/12 - 1/18=>1/v= 1/36so v = 36 cm

Thus the image is at a distance of 36 cm from the lens.The positive sign indicates it is on other side of lens as the object and so it is a virtual image.

For size.magnification formula is:m=h'/h=v/u (h'=image height,h=object height,v=image distance,u=object distance)h'/10= 36/-18h'= (36/-18) * 10h'= - 20cm

so,Position of image is 36 cm on other side of lens as object.Nature is virtual ImageSize of Image is 20 cm,which means it is magnified 2 times and is an erect image.

595.

In a optical system, two thin convex lenses usedare in contact. If the focal lengths of them are 15cm and 10 em, find the effective focal length of the7)

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effective focal length 1/F = 1/f1 + 1/f2

=> 1/F = 1/15 + 1/10=> 1/F = (2+3)/30=> 1/F = 5/30=> 1/F = 1/6=> F = 6 cm

596.

class tube 80cm long and open at both ends is half immersed inmercury. Then the top of the tube is closed and it is taken out of themercury. A column of mercury 20cm long then remains in the tube.The atmospheric pressure(in cm of Hg) isa. 80b. 70 160d. 50fe

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when we have half the tube is immersed in the mercury i.e 40 cm, the air pressure(P) inside the tube should be equal to the mercury pressure in the other half.

hence P = ρgh = ρg40

Once the tube is removed with upper end closed, the air pressure inside will remain same. Now since the other end is open, this air pressure + the pressure of mercury remaining = the atmospheric pressure at the other end.

=> P₀ = P + ρgh₁

= ρgh + ρgh₁

= ρg(40 + 20)

= 60ρg

Hence atmospheric pressure will be equal to pressure of 60cm of mercury column.

597.

Fig.7.4023 A man stands on a rotating platform, with his arms stretched horizontally holdiA man stands on a rotating5 kg weight in each hand. The angular speed of the platform is 30 revolutiminute. The manweight from the axisman together with the platform may be taken to be constant and equal to 7.6 kg m2(a) What is his new angular speed? (Neglect friction.)(b) Is kinetic energy conserved in the process? If not, from where does the changecome about?7.23ons perthen brings his arms close to his body with the distance of eachchanging from 90cm to 20cm. The moment of inertia of the

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Thank you so much

598.

Q37,If earth contracts to half of its radius, what would be the length ofthe day?

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conservation of angular momentumIw =constant for solid2/5 mR²w= constant wR²= constant 2πfR²= constant R²/T = constant so, T is directly proportional to square of radius Thus if radius is decreased to half then,T'= T/4which is 24/4time period will be 6 hours.

599.

telescope have an objective of focal length200 Cmand--an-- eyepiece-of - focal-length-8cm-Find magnifying power and length-of telescope,

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600.

6. Which of the following lenses would you prefer to use while reading smafound in a dictionary?(a) A convex lens of focal length 50 cm.(b) A concave lens of focal length 50 cm.(c) A convex lens of focal length 5 cm.(d) A concave lens of focal length 5 cm.

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