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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Substance having very small co-efficient of linear expansion, among the following is |
| Answer» ANSWER :D | |
| 2. |
A block sliding down a rough 45^(@) inclined plane has half the velocity it would have had, the inclined plane been smooth. The coefficient of sliding friction between block and the inclined plane is |
| Answer» Answer :B | |
| 3. |
A particle of mass 1 kg is moving along the line y = x + 2 (here x and y are in metres) with speed 2 m/s. The magnitude of angular momentum of particle about its origin is |
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Answer» `4 kg m^(2) s^(-1)` At x = -2 , y = 0 and at x = 0 , y = 2 The line is drawn as shown in the figure . Length of perpendicular drawn from origin to this line is `ON = r_(1) = (0 + 0 + 2)/(SQRT(1 ^(2) + 1^(2)) = sqrt2`  Angular momentum of particle about `L = m vr_(bot) = (1) (2)sqrt2 = 2 sqrt2 kg m^(2) s^(-1)` |
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| 4. |
Is the linear velocity of a particle moving with constant angular speed about non fixed axis remains constant? Why? |
| Answer» SOLUTION :No. Because the axis is NON fixed so the DIRECTION of angular velocity parallel to the axis does not remains same and hence linear velocity is also not CONSTANT. | |
| 5. |
Two blocks of mass 4kg and 6kg are connected by a string as shown in the figure. They are initially at rest on the floor. Calculate their acceleration when a force of (a) 50N (b) 100N is applied on the pulley. |
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Answer» Solution : Case(i): Force on 6KG and 4 kg object ` = (F)/(2)= 25N`. The APPLIED force on each block is less than the weight of each block. So the blocks will not move. Case (ii): A 50N Force on each block `=(100)/(2)` = 50N. The 6kg block will not move because applied force is less than its weight. On 4 kg mass RESULTANT force = mass `xx` acceleration `50-40 = 4a, 10 = 4a , a=2.5 m//s^(2)` 
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| 6. |
(A): A spring has potential energy, both when it is compressed or stretched. (R ): In compressing or stretching, work is done on the spring against the restoring force. |
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Answer» Both 'A' and 'R' are TRUE and 'R' is the CORRECT explanation of 'A's |
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| 7. |
If T_(1), T_(2) and T_(3)are the time periods of a given simple pendulum on the surface of the earth, at a depth 'h' in a mine and at an altitude 'h' above the earth's surface respectively, then |
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Answer» `T_(1)= T_(2)=T_(3)` |
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| 8. |
A uniform force of (2hat(i)+hat(j)) N acts on a particle of mass 1 kg. The particle displaces from position (3hat(j)+hat(k)) m to (5hat(i)+3hat(j)) m. The work done by the force on the particle is |
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Answer» 9J workdone ,` barW= vecF .Deltavecr= ( 2 hati+ hatj ).( 5 hati- hatk ) ` `barW = 10hatiW= 10 Nm= 10 J` |
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| 9. |
Whatwould be the change in the fundamental frequency of a stringedlnstrument if(i) the length of the string is doubled, (ii) the tension is doubled, (iii) the diameter is doubled ? |
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Answer» (ii)Frequency is proportional to the square root of the tension. So , if the tension is doubled, the fundamental frequency WOULD be `sqrt(2)` or 1 . 414 times of its INITIAL value . (iii) If the diameter is doubled, the area of CROSS section becomes`2^(2)` or 4 times the initial value.If the materials of the string is the same, the mass per unit length also becomes 4 times its original value.Thefrequency is inversely proportional to the square root of the mass per unit length.So , inthis CASE,the frequency wouldbe `(1)/(sqrt(4))`or`(1)/(2)`times, i.e., half the initial value . |
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| 10. |
When fluids are heated from the bottom, convection currents are prodcued because |
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Answer» molecular motion of FLUID BECOMES aligned |
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| 11. |
Derive an expression for the position vector of the center of mass of particle system. |
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Answer» Solution :(i) To find the centreof mass for acollection of npoint masses, say ` m_(1) , m_(2) , m_(3) …..m_(n)`we haveto firstchoosean origin and an APPROPRIATE coordinate system as shown in Figure . (ii) Let `x_(1) , x_(2) , x_(3… x_(n)`be the X-coordinates of the positions of thesepoint massesin theX direction from the origin . The equation forthe X coordinate of the centreof mass is , ` x_(CM) = ( sum m_(i) x_(i))/( sum m_(i)) ` Where ` sum m_(i)`is the totalmass M of all the PARTICELS ` ( sum m_(i) = M)` (iii)Hence ` x_(CM)= ( sum m_(i)x_(i))/(M)` (vi)Similarly,we canalsofindy and z coordinatesof the centreof mass for thesedistributedpointmassesas indicatedin Figure. ` y_(CM) = ( sum m_(i) y_(i))/( M) ` ` ( z_(CM) = ( sum m_(i)z_(i))/( M) ` (v) Hence,the position of centreof massof thesepointmassesin a CARTESIAN cooridnate system is ` ( x_(CM) y_(CM) , z_(CM))` . In general , the positionof centreof masscan be written ina vectorformas , ` vecr_(CM) = ( Sum m_(i) vecr_(i))/ M` Where` vecr_(CM) = x_(CM)= hati + y_(CM) hatj + z_(CM) hatk ` is THEPOSITION vectorof the centre of mass and` vecr_(i)= x_(i) hati + y_(i) hatj + z_(i) hatk`is the position vectorof the distributedpointmass : where ` hati , hatj and hatk ` are the unitvectorsalongX, Y and Z -axesrespectively 
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| 12. |
What is meant by 'Mechanical equilibrium ' ? |
| Answer» Solution :A SYSTEM is said to be in MECHANICAL equilibrium if no unbalanced FORCE acts on the THERMO DYNAMIC system or on the surrounding by thermodynamic system. | |
| 13. |
Three point masses of 1 kg, 2kg and 3 kg lie at (0, 0), (1, 2), (3, -1), respectively. Calculate the coordinates of the centre of mass of the system. |
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Answer» |
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| 14. |
A material has normal density r and bulk modulus B. The increase in the density of the material when it is subjected to an external pressure 'p' from all sides is |
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Answer» `(P)/(rhoB)` |
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| 15. |
The velocities of a particle performing linear SHM are 0.13 m/s and 0.12 m/s when it is at 0.12m and 0.13m from mean position, respectively. Find the period and amplitude. |
| Answer» SOLUTION :(i) 6.284 s , (II) 0.1769 m | |
| 16. |
A brass wire of length 300 cm when subjected to a force F produces an elongation "a". Another wire of twice the diameter and of same length and material, when subjected to the force F produces an elongation b. Then the value of .a/b. is |
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Answer» `1:1` |
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| 17. |
5 gm of steam at 100""^(@C is passed into calorimeter containing liquid. Temperature of liquid rises from 32^(@)C to 40""^(@)C. Then water equivalent of calorimeter and contents is |
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Answer» 40 gram |
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| 18. |
A circular disc of mass 10 kg is suspended by a wire attached to its centre. The wire is twisted by rotating the disc and released. The period of torsional oscillations is found to be 1.5s. The radius of the disc is 15 cm. Determine thetorsional spring constant of the wire. (Torsional spring constant alpha is defined by the relation J= -alpha theta, where J is the restoring couple and theta the angle of twist). |
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Answer» Solution :This QUESTION is of torsional pendulum. Its time period, `T= 2PI sqrt((I)/(alpha))` where I is the moment of inertia For disc `I = (1)/(2) mr^(2)` where m = mass of disc and r = radius of disc and `alpha =` torsional spring constant. `T^(2)= (4pi^(2)I)/(alpha)` `therefore alpha = (4pi^(2)I)/(T^2) = (4pi^(2))/(T^2)XX (1)/(2) mr^(2)` `= (2pi^(2)mr^(2))/(T^2)` `=(2XX (3.14)^(2)xx10xx(0.15)^(2))/((1.5)^(2)) = 1.97192` `therefore APPROX 1.97 (Nm)/(rad)" or "alpha approx 2.0 (Nm)/(rad)` |
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| 19. |
A body weighs 90 N on the surface of earth. Calculate the gravitational force on the body at a height equal to one-third of the radius of earth. |
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| 20. |
The centrifugal force appears to exist |
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Answer» only in INERTIAL FRAMES |
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| 21. |
An insulated container containing monoatomic gas of molar mass m is moving with a velocity v_0. If the container is suddenly stopped. The change in temperature. |
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Answer» `(mv_(0)^(2))/(3R)` |
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| 22. |
A man running on a horizontal road at 8kmph finds that rain is falling vertically. He increases the speed to 12kmphr and find that the drops make angle 30^(@) with the vertical. |
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Answer» The speed of rain is `8 sqrt(3)` kmph |
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| 23. |
The earth receives at its surface radiation from the sun at the rate of 1400" Wm"^(-2) The distance of the centre of the sun from the surface of the earth is 1.5xx10^(11) m and the radius of the sun is 7xx10^(8)m. Treating the sun as a black body, it follows from the above data that its surface temperature is ........K |
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Answer» 3925 |
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| 24. |
An equilateral prism of mass m rests on a rough horizontal surface with ceefficeinet of friction |t. A horizontal force F is applied on the prism as shown. If the coefficeient of friction is sufficiently high so that the prism does not slide before toppling, the minimum force required to topple the prism is: |
| Answer» Answer :A | |
| 25. |
A pond has a layer of ice of thickness 0.25 m on its surface the temperature of the atmosphere is 10^(@) C.Find out the time required to increase the thickness of the layer of ice 0.5 "mm". K of ice = 2 "Wm"^(-2) "K"^(-1). Density of ice = 900 "kg m"^(-3) latent heat of fusion of ice = 336 "KJ kg"^(-1). |
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Answer» |
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| 26. |
A hope of radius 2 m weights 100 kg. It rolls along a horizontal floor so that its centre of mass has a speed of 20 cm/s. How much work has to be done to stop it? |
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Answer» 4 J |
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| 27. |
An explosion breaks a rock into three parts in a horizontal plane. Two ofthem go off at right angles to each other . The first part of mass 1 kg moves with a speed of 12 m//s and the second part of mass 2 kg moves with 8 m//s. If the third part flies off with 4 m//s the speed , then its mass is |
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| 28. |
A Particle of mass 2kg is moving on a straight line under the action of force F(8-2x)N. The particle is released from rest at x = 6m. For the subsequent motion, match the following all the value in the Column-II are in their SI units): {:("Column - I", "Column - II"),("A) Equilibrium position is at x, x equal to", "P)" pi//4),("B) Amplitude of SHMs ","Q)" pi//2),("C) Time taken to go directly from x=2 to x = 4 ","R)" 4),("D)Energy of SHM is ","S)" 6),("E)Phase constant of SHM assuming equation of the form "A sin (omega t + phi),"T)" 2):} |
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| 29. |
The minimum speed of a bucket full of water whirled in a vertical circle of radius 10 m at the highest point so that water may not fall is (g=10 ms^(-2)) |
| Answer» Answer :D | |
| 30. |
In exercise 14.9 let us take the position of mass when the spring is unstretched as x = 0, and the direction from left to right as the positive direction of X-axis. Give x as a function of time t for the oscillating mass if at the moment we start the stopwatch (t = 0), the mass is (a) at the mean position. (b) at the maximum stretched position, and ( c) at the maximum compressed position. IN what way do these functions for SHM differ from each other, in frequency in amplitude or the initial phase ? |
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Answer» Solution :`a = 2 cm, omega = sqrt((k)/(m)) = sqrt((1200)/(3)) = 20 rads^(-1)` (a) When mass is at MEAN position Then x =asin `OMEGAT` x = 2 sin 20 t (b) At MAXIMUM stretched position the mass is at extreme right position, HENCE, initial phase is `(pi)/(2)` `therefore x = a sin(omegat + (pi)/(2))` ` = 2 cos omegat = 2 cos 20t` (c ) At maximum compressed position, the mass is at extreme left with initial phase of `(3pi)/(2)` rad. `therefore x = a sin(omegat + (pi)/(2))` ` = 2 cos omegat = 2 cos 20t` (c ) At maximum compressed position, the mass is at extreme left with initial phase of `(3pi)/(2)` rad. `thereforex = a sin (omegat + (3pi)/(2))` `= -a cos omegat = -2cos 20 t` Thus these functions differ in intial phase. |
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| 31. |
The-thermal capacity of 10g of a substance is 8 cal/kelvin. Its specific heat is in J/kg-K is |
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Answer» 3360 |
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| 32. |
Volume of mercury in the bulb of a thermometer is 10^(-6)m^(3). Area of cross section of capillary tube is 2xx10^(-7)m^(2). If the temperature is raised by 100^(@)C, the length of mercury column is (gamma_(Hg)=18" "10^(-5)//""^(@)C) |
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Answer» 9 cm |
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| 33. |
A metre long narrow bore held horizontally (and closed at one end) contains a 76 cm long mercury thread, which traps a 15 cm column of air. What happens if the tube is held vertically with the open end at the bottom ? |
| Answer» SOLUTION :Nearly 24 cm of mercury FLOWS out, and the remaining 52 cm of mercury thread plus the 48 cm of air above it REMAIN in EQUILIBRIUM with the outside atmospheric pressure (We assume there is no change in temperature throughout). | |
| 34. |
A stone is tied to the end of a string. When the string is whirled in a circular path, the string can never be kept horizontal. Explain the reason. |
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Answer» Solution :When astone tied to the end of a string is whirled along a HORIZONTAL circular path, the horizontal component of the tension in the string provides the necessary centripetal force and its vertical component balances the weight of the STONE. If the stone is rotated along a horizontal circular path by keeping the string horizontal, there would be no vertical component of the tension (T) in the string. In that case, the weight of the body (mg) cannot be balanced. As a result, the stone would DIP downwards leaving the horizontal circular path until the vertical component of T would be just sufficient to balance the weight of the stone. Hence, during ROTATION of the stone along a horizontal circular path, the string can NEVER be kept horizontal. 
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| 35. |
An elevator weighing 6000 kg is pulled upward by a cable with an acceleration of 10 m//s^(2). Taking g to be 10 ms^(-2), find the tension in the cable |
| Answer» Answer :A | |
| 36. |
Match Column-I with Column-II : {:("Column-I","Column-II"),("(1) It has never a positive value","(a) Escape speed"),("(2) The reason of negative potential energy of galaxy is","(b) Gravitational potential energy"),(,"(c) The type of force acting between different galaxies is attarctive"):} |
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| 37. |
Give the relation among prop,beta and gamma |
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Answer» SOLUTION :`PROP:BETA:GAMMA::1:2:3` i.e., `beta=2prop` and `lamda=3prop` and `3beta=2gamma` |
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| 38. |
A copper disc of diameter 300 mm at 20^(0)C has a concentric hole of diameter 10 cm. Determine the external and internal diameters of the disc when the temperature is raised to 60^(0)C. (alpha of copper =17xx10^(-6)//""^(0)C) |
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| 39. |
State whether the fundamental law of calorimetry is applicable in the following cases : (iii) calorimeter is kept open in air. |
| Answer» Solution :If the calorimeter is kept OPEN in AIR, heat exchange occurs with the surroundings. Hence, the fundamental LAW of calorimetry will not be APPLICABLE. | |
| 40. |
The orbital velocity of an artifical satellite in a circular orbit just above the earth.s surface is V_(0). For a satellite orbiting in a circular orbit at an altitude of half of the radius of earth is |
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Answer» `(SQRT(2//3))V_(0)` |
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| 41. |
The largest and the shortest distance of the earth from the sun are r_1 and r_2respectively. Calculate the distance from the sun when it is at perpendicular distance to major axis of the orbit drawn from the sun |
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Answer» Solution :Since `E = c/a RARR c =ea "" THEREFORE r_1 = a+c=a+ea=a(1+e)` ` r_2 = a -c =a -ea = a (1-e)` Required distance`L = (b^2)/(a)` (semi latus rectum ) we have `r_1+r_2 = 2a` and `r_-r_2 =a(1+e) -a(1-e) = 2ae rArr e= (r_1-r_2)/(r_1+r_2)` Also `b^2 = a^2 (1-e^2)` ` therefore L = (b^2)/(a) = (a^2 (1-e^2))/(a) = a (1-e^2)` ` = ((r_1+r_2)/(2)) [1-((r_1-r_2)/(r_1+r_2))^2]` on simplification , `L = (2r_1r_2)/(r_1+r_2) "or " 2/L = (1)/(r_1) + (1)/(r_2)` |
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| 42. |
A force vec(F) = (hat(i) - hat(j))N acts on a particle which moves with a velocity vec(V) = (-2 hat(i) - 3 hat(k)) m//s. Find the power delivered by the force. Usie the formula P = vec(F).vec(v) |
| Answer» Answer :A | |
| 43. |
It is possible to project a particle with a given velocity in two possible ways so as to make them pass through a point P at a horizontal distance r from the point of projection. If t_(1) and t_(2) are time taken to reach this point in two possible ways, then the product t_(1) t_(2) is proportional to |
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Answer» `(1)/( R)` |
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| 44. |
A raindrop falls near the surface of the earth with almost uniform velocity because |
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Answer» its WEIGHT is negligible |
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| 45. |
A cube of uniform density and edge a is balanced on a cylindrical surface of radius r. Shown that the criterion for stability of equilibrium of the cube, assuming that fraction is sufficient to prevent slipping, is r gt a//2 |
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Answer» |
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| 46. |
A liquid is filled into a semielliptical cross-section with 'a' as semi major axis and 'b' as semi minor axis. The ratio of the surface tension forces on the curved part and the plane part of the tube in. vertical position will be |
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Answer» `(PI (a +B))/( 4 b)` |
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| 47. |
"Displacement vector is basically a position vector". Comment on it. |
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Answer» <P> Solution :This statement is almost correct only. Because the displacement vector also gives the position of a POINT just LIKE a position vector. The difference between these TWO vectors is p. The displacement vector gives the position of a point with respect to a point other than ORIGIN but position vector gives the position of a point with respect to origin. |
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| 48. |
Which basic properties are needed for the system being oscillate? |
| Answer» SOLUTION :INERTIA and ELASTICITY. | |
| 49. |
Twoideal Carnot engines opeate in cascade (all heat given up by one engine is used by the other engine to produce work) between temperatures T_(1) and T_(2). The temperature of the hot reservoir of the first engine is T_(1) and the temperature of the cold reservoir of the second engine is T_(2). T is the temperature of the sink of first engine which isi also the source for the second engine. How is T related to T_(1) and T_(2) if both the engines perform equal amount of work? |
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Answer» `(2T_(1)T_(2))/(T_(1) + T_(2))` `Q_(L)`= Heat extracted from first engine `Q._(L)`= Heat extracted from `2^(nd)` engine WORK done by first engine= work done by SECOND engine `Q_(H)- Q_(L) = Q_(L)- Q._(L)` `:. Q_(H)+ Q._(L) = 2Q_(L)` but `Q_(L) prop T and Q._(L) prop T_(2) "ALSO" Q_(H) prop T_(1)` `:. T_(1) + T_(2) = 2T` `:. T= (T_(1) +T_(2))/(2)` |
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| 50. |
A square plate of moment of inertia 'I' is pivoted at centre. It has small projection of neglegible mass to one of its sides. A particle of mass 'm' moving with a velocity v parallel to the side having projection strikes to projection and stricks to it. If 'l' is the side length, the angular velocity of plate is |
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Answer» `("mvl")/(2[I+("ml"^(2))/(4)])` |
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