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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. |
To show that a simple pendulum is in a simple harmonic motion it is necessary to assume that |
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Answer» the length of the pendulum is small |
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| 2. |
Which of the following relations is not correct? |
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Answer» `B=mu_(0) (H+1)` |
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| 3. |
What is the length of the pendulum of a clock which beats seconds, given that the acceleration due to gravity at the place is equal to 9.8 ms^(-2). |
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Answer» Solution :The period of SIMPLE PENDULUM is given by `T= 2pisqrt((l)/(G))implies` The length of the pendulum `= 1= (GT^(2))/(4pi^(2)) implies l= (9.8 xx 2^(2))/(4 xx (3.14)^(2))` `l=(9.8 xx 2^(2))/(4 xx 9.86)= 0.994 m~=1m` |
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| 4. |
Water is flowing streamline motion through a tube with its axis horizontal. Consider two points A and B in the tube at the same horizontal level. a) The pressure at A and B are equal for any shape of the tube. b) The pressure are never equal. c) The pressure are equal if the tube has nonuniform cross-section. d) The pressure may be equal even if the tube has a nonuniform cross-section. |
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Answer» B and c are CORRECT |
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| 5. |
A body is in pure rotation. The linear speed v of the particle, the distance r of the particle from the axis and the angular velocity roof the body are related as omega =v/r. Then |
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Answer» `OMEGA ALPHA(1)/(R )` |
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| 6. |
If wavelengths of maximum intensity of radiations emitted by the sun and the moon are 0.5xx10^(-6) m and 10^(-4) m respectively, the ratio of their temperatures is |
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Answer» `1//100` |
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| 7. |
The expression for maximum height attained when the body is projected at an angle with the horizontal is : |
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Answer» `(U SIN THETA)/(2G)` |
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| 8. |
A sound of frequency 1500 Hz is emitted by a source which moves away from an observer and moves towards a cliff at a speed of 6 ms^(-1) (a) Calculate the frequency of the sound which is coming directly from the source. (b) Compute the frequency ofsound heard by the observer reflected off the cliff. Assume the speed of sound in air is 330 ms^(-1) |
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Answer» Solution :(a) SOURCE is moving away and observer is stationary, therefore, the frequency of soundheard DIRECTLY from source is `f. = (f)/((1 + (v_(s))/(v))) = (1500)/((1 + (6)/(330))) = 1473` Hz ( b) Sound is REFLECTED from the cliff and REACHES observer, therefore, `f. = (f)/((1 - (v_(s))/(v))) = (1500)/(( 1- (6)/(330))) = 1528 Hz` |
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| 9. |
(A) : Shake and light year, both measure time (R) : Both velocity and velocity of light have same dimensions. |
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Answer» Both (A) and (R) are true and (R) is the CORRECT EXPLANATION of (A) |
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| 10. |
50gm of water and an equal volume of alcohol (sp.gravity = 0.8) are placed one after another in a calorimeter of water equivalent 2gm. They are found to cool from 60^(@)C to 55^(@)C in 2 min. and 1 min respectively. The sp. Heat of Alcohol in "Cal " gm^(-1)""^(@)C^(-1) is |
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Answer» 0.1 |
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| 11. |
A light bar of length 2 m is suspended horizontally by means of two wires of equal lengths connected to its two ends. One wire is of steel having a cross sectional area of 0.1 cm^2, the other is of brass with a cross sectional area of 0.2 cm^2,Find the point on the bar from where a weight must be suspended so that both the wires experience (i) the same stress,(ii) the same strain, Given the young's modulus for steel =2 times 10^11 N.m^-2 and that for brass =10 times 10^10 N.m^-2. |
Answer» Solution :Let the horizontal bar be AB (fig.1.14). A LOAD W is HUNG from the point C. Let AC be x. In this condition, let the tension in the steel wire be `T_1` and that in the brass wire be `T_2`.  Stress on the steel wire `=T_1/alpha_1` and stress on the brass wire=`T_2/alpha_2`. (i) IF the stresses in both the wires are the same, then `T_1/(0.1times10^-4)=T_2/(0.2times10^-4)or,T_1/T_2=1/2`.....(1) Since the system is in EQUILIBRIUM, taking moments about the point C, we get `T_1x=T_2(2-x)or,T_1/T_2=(2-x)/x` `therefore1/2=2/x-1or,2/x=3/2or,x=4/3=1.33m` So the weight should be suspended at a distance of 1.33m from the steel wire. (ii) Longitudinal strain `=(LONGITUDI na l stress)/Y` `=(T/a)/Y=T/(aY)` For the same strain in the two wires, `T_1/(0.1times10^-4Y_1)=T_2/(0.2times10^-2 Y_2)` or,`T_1/T_2=(0.1times10^-4times2times10^11)/(0.2times10^-4times10times10^10)=1thereforeT_1=T_2` Since the system is in equilibrium, taking moments about the point C, we get, `T_1x=T_2(2-x)or,x=2-xor,x=1m` So, the weight should be suspended from the mid-point of the horizontal bar. |
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| 12. |
Two bodies are projected from the same point in the directions making an angle alpha_1 and alpha_2 with horizontal and strike at the same point in the horizontal plane through a point of projection. If t_1 and t_2are their time of flights. Then (t_1^2 - t_2^2)/(t_1^2 + t_2^2)= |
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Answer» `(TAN (alpha_1 - alpha_2))/(tan (alpha_1 +alpha_2))` |
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| 13. |
At what rate is the energy radiated by a sphere of radius 5 cm at 3000K and with an emissivity of 0.3 ? ( given Stefan's constant = 5.7 x 10^(-8)Wm^2K^(-4)) |
| Answer» SOLUTION :`43.53 XX 10^(3) W` | |
| 14. |
The relation between U, P and V for an ideal gas is U = 2 + 3PV. What is the adiabatic coefficient of gas. |
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Answer» 1.33 |
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| 15. |
Two identical ball bearing in contact each other and resting on a frictionless table are hit head - on by another ball bearing of the same mass moving intially with a speed c as shownin figure . If the collision is elastic mwhich of the following (figure ) is a possible result after collision ? |
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Answer»
When ball 1 collides with ball -2 ,then `v_(1)=0 and v_(2)=v` Similarly, when ball 2 collides with ball 3, `v_(2)=0 and v_(3) = v` |
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| 16. |
A lorry and a car moving with the same momentum are brought to rest by the application of brakes , which provide equal retarding force . Which of them will come to rest in shorter time ? Which will come to rest in less distance ? |
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Answer» LORRY will COME to rest in a shorter distance |
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| 17. |
A boy is swinging on a swing such that his lowest and highest positions are at heights of 2m and 4.5m respectively. His velocity at the lowest position is, |
| Answer» Answer :B | |
| 18. |
The length of an organ pipe open at two ends is twice that of another organ pipe closed at one end . If the fundamentalfrequency of the open pipe is 100 Hz , find out the frequency of the 3rd harmonic emitted by the closed pipe . |
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Answer» Solution :The fundamental frequency of the open pipe, `n_(0^(.)) = (V)/(2l),so V = 2ln_(0^(.))`[V = velocity of sound in air, l = LENGTH of the open pipe] The length of the closed pipe is `(l)/(2)`. So the frequency of the3rd harmonic is ` n = 3 xx ` fundamental frequency `= 3n_(0) = 3* (V)/(4(1/2))=(3.2V)/(4)` `=(3xx2xx2ln0^(.))/(4l)=3n_(0)^(.)` ` = 3 xx 100 = 300 ` Hz . |
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| 19. |
Two small spheres of masses 10 kg and 30 kg are joined by a rod of length 0.5 m and of negligible mass. The M.I of the system about a normal axis through centre of mass of the system is |
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Answer» `1.875 KGM^(2)` |
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| 20. |
When a mass is suspended on a metallic wire, the length of the wire increases slightly. Name and state the law that relates to the restoring force developed in the wire and its deformation. |
| Answer» SOLUTION :Hooke.s LAW | |
| 21. |
Calculate the self-gravitational potential energy of matter forming a. a thin uniform shell of mass M and radius R, b. a uniform sphere of mass m and radius R. |
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Answer» SOLUTION :In the PROCESS of formation of body, work has to be DONE by an external agent bit by bit to build up the body. This energy of the external agent is stored as gravitational energy. This is called te self -gravitation potential ennergyy or gravitational energy of mutual gravitational interaction. a. Consider a sphere of any radius `x`. Mass of the sphere `=4pi//3x^(3)rho` where `rho=` density of mass Gravitation potential of the surface `=-4pi//3Grhox^(2)` This is also the work done in adding unit mass to the sphere by the external agent. when the thickness is increased by `dx`, mass added by the agent is `4pix^(x)dxrho`. Therefore, work done by agent in INCREASING the surface from `x` to `x` is `dx` `(-(4pi)/3grhox^(2))(4pix^(2)xrho)=(16pi^(2))/3Grho^(2)x^(4)dx` Therefore, total work done by the agent `=-(16pi^(2)Grho^(2))/3 int_(0)^(R)x^(4) dx=-(16pi^(2)rho^(2)R^(5))/15` Now, `rho=m/((4pi)/3R^(3))=(3m)/(4piR^(3))` Therefore, `U` (self-energy)`=-(16pi^(2)R^(5)G)/15xx(9m^(2))/(16pi2R^(6))` `=-3/5(GM^(2))/R` b. Consier the shell when mass `m` has already been piled up by the agent. Then, potential of the shell `=-GM//R` This is also the work done by the agent in adding another unit mass to the shell. Therefore, the elementary work done in adding an elementary mass `dm` is `-Gm//R dm`. Therefore, `U` (self-potential energy)`=-1/2Gm^(2)//R` |
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| 22. |
Simple harmonic motion is a periodic motion, but all periodic motions are not simple harmonic' - explain. |
| Answer» Solution :The MOTION that repeats itself at REGULAR intervals of time is CALLED periodic motion. If the periodic motion is (1) linear and (2) the acceleration of the particle executing the motion is proportional to its displacement from the position of equilibrium and is always directed towards the mean position, only then the motion of the particle is said to be simple harmonic. The motion of the HANDS of a clock or the motion of the planets and satellites are periodic in nature. But as these MOTIONS do not satisfy the above conditions, they cannot be called simple harmonic. So it can be said that all simple harmonic motions are periodic but all periodic motions are not simple harmonic. | |
| 24. |
In problem 15 if a motor-cyclist passes over the bridge at 18 ms^(-1), atb which point will the reaction become equal to zero ? |
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Answer» |
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| 25. |
(A) : A body can possess mechanical energy without momentum.(R ) : A bent bow potential energy by virtue of deformation. |
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Answer» Both (A) and (R ) are TRUE and (R ) is the correct explanation of (A) |
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| 26. |
A car moves uniformly along a horizontal sine curve y = a sin (x//alpha) where x and alpha are certain constants. The coefficient of friction between the wheels and the road is equal to mu. Velocity of the car riding without sliding is V le alphasqrt((mugx)/(a)) then x= ................. |
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Answer» |
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| 28. |
Weighing the earth : You are given the following data: g=9.81 ms^(-2). R_E= 6.37xx10^6 m , the distance to the moon R=3.84xx10^8 m and the time period of the moons revolution is 27.3 days.Obtain the mass of the earth M_E in two different ways. |
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Answer» Solution :We KNOW that `M_E=(gR_E^2)/G=(9.81xx(6.37xx10^6)^2)/(6.67xx10^(-11))=5.97xx10^24` kg The moon isa satellite of the Earth. According toKepler.s THIRD law `T^2=(4pi^2R^3)/(GM_E) M_E=(4pi^2R^3)/(GT^2)` `=(4xx3.14xx3.14xx(3.84)^3xx10^24)/(6.67xx10^(-11)xx(27.3xx24xx60xx60)^2)=6.02xx10^24` kg Both methods YIELD almost the same answer, the difference between them being less than 1%. |
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| 29. |
Explain in detail the four different types of oscillations. |
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Answer» Solution :Damped oscillations : (i) Due to the presence of friction and air drag, the amplitude of oscillation decrease as time progresses. (II) It implies that the oscillation is not sustained and the energy of the SHM decreases gradually INDICATING the loss of energy. (iii) The energy lost is absorbed by the surrounding medium. This type of oscillatory motion is known as damped oscillation. (iv) The motion of the oscillator is said to be damped the resistive force (or damping force) is proportional to the velocity of the oscillator.  Examples (i) The oscillations of a pendulum. (ii) Electromagnetic oscillations in a tank circuit. (iii) Oscillations in a dead beat and ballistic galvanometers. Maintained oscillations: (i) While playing in swing , the oscillations will stop aftera few cycles, this is due to damping. (ii) By supplying energy from an external SOURCE , the amplitude of the oscillation can be made constant . Such vibrations are known as maintained vibrations. Example : The vibration of a turning fork getting energy from a battery or from external power supply. Forced oscillations : (i) Any oscillator driven by an external periodic agency to overcome the damping is known as forced oscillator or driven oscillator. (ii)In this type of vibration , the body executing vibration initially vibrates with its natural frequency and due to the presence of external periodic force, the body later vibrates with the frequency of the body later vibrates with the frequency of the APPLIED periodic force. (iii) Such vibrations are known as forced vibrations. Example : Sound boards of STRINGED instruments. Resonance : (i) It is a special case of forced vibrations where the frequency of external periodic force (or driving force) match with the natural frequency of the vibrating body (driven). (ii) As a result the oscillating body begins to vibrate such that its amplitude increases at each step and ultimately it has a large amplitude . Such a phenomenon is known as resonance and the corresponding vibrations are known as resonance vibrations. Example : The breaking of glass due to sound. |
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| 30. |
What is the basic difference between classical Physics and Quantum Mechanics ? |
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Answer» Solution :Classical Pyhsics deals with mecorscopic phenomena, where PARICLE size `gt 10^(-8) m` and particle velocity `lt lt10^8 m//s`. Gravitational forces and electromagnetic forces are sufficient to EXPLAIN such phenomena. Quantum Mechanisc deals with microscopic phenomena on the SCALE of atoms, molecules, nuclei. Here, the WEAK and strong nuclear forces become DOMINANT. |
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| 31. |
How much work is done in circulateing a small object of mass m around a sphere of mass m in a circle of radius R. |
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Answer» |
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| 32. |
Which of the following affects the elasticity of a substance |
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Answer» HAMMERING and annealing |
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| 33. |
A monkey of mass m clings to a rope over a fixed pulley. The opposite ends of the rope is tide to a weight of mass M lying on a horizontal plate neglecting friction, find the acceleration of both bodies relative to the plate and tension of the rope in the following cases: i) the monkey does not move with respect to rope. ii) the monkey moves upwards with respect to rope with acceleration beta . iii) the monkey moves downwards with respect to the rope with acceleration beta. |
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Answer» Solution :i) If the monkey is at rest on the rope, then acceleration of both mass M and monkey are same, equal to a (SAY) If T is TENSION in the rope, then the equation of MOTION of monkey is ` mg-T=ma_1`..........(1) and equation of motion of massM is `T = Ma_1` ........... (2) Adding (1) and (2) `mg =(M+m)a_1` ` :. a_1 = (m)/(M+m) g ` ......... (3) ii) When monkey moves upward with acceleration `BETA`, the reaction m `beta` acts downward, therefore equations of motion now take the form (`a_2` is acceleration of mass, M relative to plate) ` mg + m beta - T = ma_2` ( for monkey ) ............. (4) ` T= Ma_2 ` ( for mass M) ............. (5) Adding , we get , `mg + m beta = ( M+ m)a_2` `:. a_2 =(m (g + beta))/( M + m)` ` :.` The acceleration of mass relative to plane ` a_2 = ( m ( g + beta))/( M + m)` ............ (6) and acceleration of monkey M relative to plate `a_2 = a_2 - beta = (m (g + beta))/( M + m) - beta = ( m(g + beta ) - beta ( M + m))/( M+ m) = (mg + m beta - M beta - m beta)/( M + m) = ( Mg - M beta)/( M + m)` iii) When monkey moves downward with acceleration `beta`, the reaction `(R= mbeta)` acts upward, therefore the equations of motion take the form (`a_3` is acceleration of block relative to plate) `mg - m beta -T = ma_3` .......... (8) `T = Ma_3 ` ............ (9) Adding we get ` mg - m beta = (M + m) a_3` ` :. a_3 =( m (g - beta))/(M+ m)` and acceleration of monkey relative to plate ` a_3^1 = a_3 + beta = (m ( g -beta))/( M +m) + beta = (mg - m beta + M beta + m beta )/( M + m)` `:. a_3^(1) = (mg + M beta )/( M + m)` |
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| 34. |
A disc of moment of inertia la is rotating in a horizontal plane about its symmetry axis with constant angular speed co. Another discinitially at rest of moment of inertia I, is dropped coaxially on to the rotating disc. Then, both the discs rotate with same constant angular speed The loss of kinetic energy due to friction in this process is, |
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Answer» `(1)/(2) (I_(B)^(2))/((I_(a)+I_(b)))OMEGA^(2)` |
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| 35. |
Two bodies are projected with the same speed. If one is projected at an angle of30^@and other at 60^@ to the horizontal. Then the ratio of maximum heights |
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Answer» `3:1` |
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| 36. |
Force acting on a particle is (2hati+3hatj)N. Work done by the force is zero, when a particle is moved along the line 3y+kx=5. Here the value of k is |
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Answer» 2 |
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| 37. |
Mark the correct statements for a particle going on a straight line : a) If the velocity and acceleration have opposite sign, the object is slowing down. b) If the position and velocity have opposite sign, the particle is moving towards the origin. c) If the velocity is zero at an instant, the acceleration should also be zero at that instant. d) If the velocity is zero for a time interval, the acceleration is zero at any instant within the time interval. |
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Answer» a, B & C are correct |
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| 38. |
A one litre flask contains some mercury. It is found that at different temperature s, the volume of air inside the flask remains the same. What is the volume of mercury in the flask? Glass, a = 9 xx 10 ^(-6) // K and gammafor mercury =1.8 xx 10 ^(-4) //K. |
| Answer» SOLUTION :`150 CC.` | |
| 39. |
An engine has an efficiency of 0.25 when temperature of sink is reduced by 58^(@)C, if its efficiency is doubled, then the temperature of the source is |
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Answer» `150^(@)C` |
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| 40. |
Conservation of momentum in a collision between particles can be understood from |
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Answer» conservation of energy By Netwon.ssecondlawfor systemof particles If`F_(ext ) = 0` `0=(d p)/( dt )` `dp = 0` p= constant Momentum of systemwill beconservedif externalforce actingon systemiszero . In CASEOF COLLISION of particleaccordingto Newton.sthird lawof motionequal andoppositeforce willact on individualparticlesHencetotalforceon thesytemwill be ZERO. |
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| 41. |
If L, C, R represent inducatance, capaitance and resistance respectively, the combinations having dimensions of requency are : |
| Answer» Answer :A::C | |
| 42. |
A body on the surface of the earth at latitude 60^(@) will be under weight lessness state if the angular velocity of rotation of the earth becomes |
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Answer» `SQRT((GM)/(R^(3)))` |
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| 43. |
The distance between the two nucleii of HCl is 1.27A. If the mass of chlorine atom is 37 times that of Hydrogen, the centre of mass of the system from the Hydrogen nucleus is |
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Answer» `1.1A` |
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| 44. |
The following plot shows the variation of potential energy (U) of a system versus position (x). From the graph we can interpret that : |
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Answer» Point D is POSITION of neutral equilibrium |
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| 45. |
Consider the following statement. The internal energy of an ideal monoatomic gas may have contributions from: |
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Answer» translation KINETIC energy of its molecules |
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| 46. |
The equation motion of a particle is SHM is a+16pi^(2)x=0. In the equation a is the linear acceleration (in m//sec^(2)) of the particle at a displacement x in meter. The time period of SHM in seconds is |
| Answer» ANSWER :B | |
| 47. |
A 2 g ball of glass is released from the edge of a hemispherical cup whose radius is 20 cm. What is the speed of the ball when it reaches the bottom of the cup? (Take g = 10 m s^(-2)) |
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Answer» `2 m s^(-1)` kinetic energy at A + potential energy at A = kinetic energy at B + potential energy at B `:. 0 + mgh = 1/2 mv^2 + 0` or `v^2= 2gh = 2 XX 10 xx 0.20 = 4` `[ :. h = "RADIUS" = 20 cm = 0.2 m]` or `v = 2 ms^(-1)` 
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| 48. |
A uniform sphere of mass m and radius r rolls without sliding over a horizontal plane, rotating about the horizontal axis OA. In the process. Centre of sphere moves with velocity v along a circle of radius R. Total KE of the sphere is : (omega_(v),I_(v) are angular velocity and moment of inertia about vertical axis respectively) |
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Answer» greater than `1/2mv^(2)` |
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| 49. |
Molar heat capacity of a gas does not dependon a) Its temperature b) Its molecular weight c) Its atomicity |
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Answer» a and B are TRUE |
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| 50. |
To keep a piece of paper horizontal, you should blow over, not under it. Why? |
| Answer» Solution :When air is blown over it, VELOCITY BECOMES high and pressure becomes low by Bernoulli.s THEOREM. But the pressure below the paper becomes high and the paper is raised and may become HORIZONTAL | |
