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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. |
Discuss conservation of angular momentum with example. |
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Answer» Solution :(i) According to law of conservation of angular momentum, when no external torque acts on the body, the NET angular momentum of a rotating rigid body remains constant. i.e. If `tau = (dL)/(dt) = 0`, L = Constant (ii) But L = `I omega`, So that, `I omega` = Constant or `I alpha (1)/(omega)` (iii) It shows that if the moment of inertia I increses, the angular velocity `omega` decreases and vice versa. Example : The ice dancer spins slowly when the hands are stretched out as this POSITION INCREASES moment of inertia and spis faster when the hands are brought close to the body as it decreases moment of inertia as shown in figure.  A diver while in AIR increases the number of somersaults by curling his body close, to decrease the moment of inertia moment of inertia as shown in figure. 
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| 2. |
Which of the following is not the characteristic of turbulent flow |
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Answer» VELOCITY more than the CRITICAL velocity |
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| 3. |
A drop of water of surface area A and radius R at a temperature T breaks into two drops of area A_(1) and A_(2), radii r_(1) and r_(2) and having temperature T_(1) and T_(2). Then the correct statement is |
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Answer» `A=A_(1)+A_(2)` |
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| 4. |
A rope thrown over a pulley has ladder (of mass M - m) with a man of mass m on one of its ends and a counterbalancing mass M on its other end The man climbs with a velocity v_(r ) relative to a ladder. Pulley and rope are ideal. The velocity of centre of mass of the system is |
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Answer» `(m)/(M)v_(R )` |
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| 5. |
Statement I: A needle placed carefully on the surface of water may float, whereas a ball of the same material will always sink. Statement II: The buoyancy of an object depends both on the material and shape of the object. |
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Answer» STATEMENT I is true, statement II is true , statement II is a correct explanation for statement I. |
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| 6. |
The angle between two vectors -3hati+6hatkand2hati+3hatj+hatk is |
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| 7. |
Two bodies of masses m and 4 m are moving with equal kinetic energies. The ratio of their linear momenta is |
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Answer» `1:2` |
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| 8. |
A ball rolls without slipping. The radius of gyration of the ball about an axis passing through its centre of mass is K. If radius of the ball be R, then the fraction of total energy associated with its rotational energy will be ………….. |
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Answer» `(R^(2))/(k^(2)+R^(2))` Rotational kinetic energy = `(1)/(2)Iomega^(2)` `=(1)/(2)mk^(2)omega^(2)(because I=mK^(2))` and linear kinetic energy `=(1)/(2)MV^(2)` `=(1)/(2)mR^(2)omega^(2)(because v=Romega)` `THEREFORE` Fraction associated with rotational motion = `("Rotational kinetic energy")/("Total kinetic energy")` `=("Rotational kinetic energy")/("Rotational kinetic energy + linear kinetic energy")` `=((1)/(2)mk^(2)omega^(2))/((1)/(2)mk^(2)omega^(2)+(1)/(2)mR^(2)omega^(2))` `=(k^(2))/(k^(2)+R^(2))` |
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| 9. |
A rod weighin W is placed horizontally over knife edges A and B. Distance between the knife edges is d and the distance of the centre of gravity of the rod from Ais x. What are the reactions at A and B? |
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Answer» |
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| 10. |
A solid sphered is projected up along an inclined plane of inclination 30^(0) with the horizontal with a speed of 4 ms^(-1) If it rolls without slipping, the maximum distance traversed by it is (g=01 ms^(-2)) |
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Answer» `1.12 m` |
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| 11. |
A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of water in the capillary tube is 5g. Another capillary tube of radius 2r is immersed in water. The mass of water that will rise in this tube is |
| Answer» ANSWER :C | |
| 12. |
Bag andsuitcase have broad (wide) handle why ? |
| Answer» SOLUTION :Area of BROAD handle is large so , when suitcase is lifted the pressure on the SURFACE of plam felt LESS. | |
| 13. |
Two glass plates are separated by a thin layer of water of thickness 0.01 mm. If the wetted area corresponding to each plate be 30cm^(2), calculate the force required to pull the plate apart. Surface tension of water is 75 dyne/cm. |
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Answer» |
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| 16. |
In a double star system , two stars of masses m_(1) and m_(2) seperated by a distance d rotate about about their centre of mass. Then their common angular velocity would be |
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Answer» `sqrt((Gm_(1))/(d^(3)))` |
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| 17. |
A piece of brass (Cu and Zn) weighs 12.9 g in air. When completely immersed in water, it weights 11.3 g. The relative densities of Cu and Zn are 8.9 and 7.1 respectively. Calculate the mass of copper in the alloy |
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Answer» `6.6gm` |
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| 18. |
Solve the following and express the result to an appropriate number of significant figures. (iii) 75.5xx125.2xx0.51 |
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Answer» SOLUTION :`75.5xx125.2xx0.51=4820.826` = 4800 (Rounded off UPTO two significant FIGURES) |
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| 19. |
Whichof the followng pair is correct with respect to the dimensions of two quantities having same dimentions ? |
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Answer» force and momentum |
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| 20. |
Choose the old man out from the following equations of motion. |
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Answer» V = U + at |
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| 21. |
A 1kg ball is rotated in a vertical circle by using a string of length 0.1m. If the tension in the string at the lowest point is 29.4N, its angular velocity at that position is |
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Answer» `7 "RADS"^(-1)` |
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| 22. |
The force required to tow a car at constant velocity is directly proportional to velocity. If it requires 160 W to two a car with a velocity of 4ms^(-1), the power it required to move the car with a velocity of 9ms^(-1) is |
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Answer» 900W |
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| 23. |
While measuring acceleration due to gravity by asimple pendulam a student makes a positive error of 1% in length and a negetive error of 3% in the value of timeperiod . The actual percentage of error in the measurement is |
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Answer» 0.02 |
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| 24. |
A body is initially at rest. It undergoes one dimensional motion with constant acceleration. The power delivered to it at time t is proportional to |
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Answer» <P>`t^(1//2)` As power , `P = F xx v :. P = (ma) xx at = ma^2 t` As m and a are CONSTANTS, `:.` P prop t` . |
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| 25. |
The electric field of an electromagnetic wave changes with time as E=K(1+cosOmega t) cos omega t, where Omega= 5xx10^(15) s^(-1), omega= 2xx10^(16) s^(-1) and K is constant. This radiation is incident on a sample of hydrogen atoms initially in ground state. Assume that atoms absorb light as photons. neglecting recoil of hydrogen nucleus on ionisation, what will be the energy of ejected electrons from hydrogen. [The ionisation energy of hydrogen atom= 13.6 eV and h=2pi xx 6.6xx 10^(-16) eV-s] |
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Answer» 0.7eV The three terms CORRESPOND to photons of energies `h omega, h(omega-Omega)` and `h(omega-Omega) ` . The LATTER exceeds the ionisation by 2.9 eV . that DIFFERENCE equals ejected electrons energy. |
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| 26. |
Two balls of the same mass, one of iron and the other of copper, are dropped from the same height. Which one would become hotter? |
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Answer» Solution :As the mass and the HEIGHT of both BALLS are the same, the initial potential energy (= mgh) is the same for both the balls. So the kinetic energy on impact with the ground will also be the same. Then, the same amount of heat will produced . We know that, increase in TEMPERATURE = `("heat produced")/("mass" xx "specific heat")` But the specific heat of copper is lower than that of IRON. So the copper ball will be HOTTER due to itshigher rise in temperature. |
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| 27. |
A spring of force constant k is cut into length of ratio 1 : 2 : 3. They are connected in series and the new force constantis k'. Then they are connected in parallel and force constant is k''. That k' : k'' = ………….. |
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Answer» The length of spring segments `= (l)/(6),(2l)/(6),(3l)/(6)` respectively. Now, `k propto (l)/(l)` `(k_1)/(k)= (l)/(l_1) implies k_(1)= (kl)/(l_1)= (kl)/((l)/(6))= 6k` and `(k_2)/(k)= (l)/(l_2) implies k_(2)= (kl)/(l_2)= (kl)/((l)/(3))= 3k` and `(k_3)/(k)= (l)/(l_3) implies k_(3)= (kl)/(l_3)= (kl)/((l)/(2))= 2K` For series connection `(1)/(k.)= (1)/(6k) + (1)/(3k)+ (1)/(2k) = (1)/(k)` `THEREFORE k.= k"""........."(1)` and for parallel connection `k..= 6k+3k+2k` `therefore k..= 11k """........"(2)` `therefore (k.)/(LK..)= (1)/(11)`. |
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| 28. |
The period of a simple pendulum measured inside a stationary lift is 'T'. If the lift starts moving upwards with a acceleration g // 3. What will be the time period |
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Answer» `T//3` |
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| 29. |
Aman of 50kg is standing at one end on a boat of length 25m and mass 200kg. If he starts running and when he reaches the other end, he has a velocity 2ms with respect to the boat. The final velocity of the boat is (in m s^(-1)) |
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Answer» `(2)/(5)` |
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| 30. |
The pair of physical quantities have the same dimensional formula are |
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Answer» MOMENTUM, impulse |
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| 31. |
A wooden object the same in water in a beaker. The object is near a side of the beaker as shown in figure. Let P_(1),P_(2),P_(3) be the pressure at the three points A, B and C of the bottom as snown in the figure. |
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Answer» `P_(1)=P_(2)=P_(3)` |
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| 32. |
Round off to the number 12.653 upto 3 digits: |
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Answer» 12.5 |
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| 33. |
The density of the material of a hollow sphere of radius R is rho. Prove that the sphere can float on water if the thickness (t) of its wal satisfies the relation : tleR/(3rho). |
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Answer» Solution :According to the condition of floatation, weight of the SPHERE `le` weight of the same volume of water or, `[4/3piR^(3)-4/3pi(R-t)^(3)]rhole4/3piR^(3)xx1` or, `[4/3piR^(3)-4/3piR^(3)(1-t/R)^(3)]rhole4/3piR^(3)` or, `4/3piR^(3)[1-(1-t/R)^(3)]rhole4/3piR^(3)` or, `[1-(1-(3t)/R)]rhole1""[tleR,"terms CONTAINING "t^(3)/R^(3),t^(2)/R^(2)" are neglected"]` or, `(3t)/Rrhole1or,tleR/(3rho)`. |
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| 34. |
A river is of width 120m which flows at a speed pf 8 ms^(-1). If a man swims with a speed of 5ms^(-1) at angle of 127^(@) with the stream, his drift on reaching other bank is |
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Answer» 50 m |
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| 35. |
An ideal gas has volume V_0 at 27^@C . It is heated at constant pressure so that its volume becomes 2V_0. The final temperature is |
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Answer» `54^@C` |
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| 36. |
In a hypothetical arrangement two hollow glass balls are connected by a tube, which has a mercury pellet in the middle. If this arrangement is proposed to measure the 'temperature of the surroundings and act like a thermometer, then you propose to |
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Answer» Place the stationary tube horizontal and the marked readings can GIVE the required temperature. |
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| 38. |
In previous problem what is the angular speed of S_(2) is the observed by an astronaut in S_(1) when they are closet : |
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Answer» `(PI)/(2)` |
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| 39. |
A wooden cylinder floats in water with length h immersed into it. If it is pushed a little inside water and then released, show that it will perform a simple harmonic motion. Calculate the time period of this motion. |
Answer» Solution :Let the cross-sectional area of the cylinder be `alpha`. ACCORDING to Archimedes. principle,  weight of the cylinder = weight of the displaced water at equilibrium = `halpharhog," "[rho="DENSITY of water"]` `therefore` Mass of the cylinder, `m=halpharho` If the cylinder is pushed through a distance x inside the water, then an extra buoyant force ACTS on the cylinder in the upward direction. It tries to bring the cylinder BACK to its equilibrium POSITION. So the restoring force, F = extra buoyant force = weight of the extra water displaced = `-xalpharhog` `therefore` Acceleration of the cylinder, `a=F/m=(-xalpharhog)/(hrhog)=(-g)/h*x=-omega^(2)x" "["where "omega=sqrt(g/h)]` As the motion of the cylinder obeys the equation `a=-omega^(2)x`, it is simple harmonic. Time period of the motion, `T=(2pi)/omega=2pisqrt(h/g)`. |
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| 40. |
The magnitude of exernal force required to produce unit acceleration in the body is equal to ………. of the body. |
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Answer» |
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| 41. |
What is effect of tensile force on lateral dimensions ? |
| Answer» Solution :When BODY is under the effect of tensile force, its length increases and hence its lateral dimensions LIKE DIAMETER or radius decreases. | |
| 42. |
(A) : When a particle moves in a circle with a uniform speed, its velocity and acceleration both changes. ( R) : The centripetal acceleration in circular motion is dependent on angular velocity of the body. |
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Answer» Both (A) and ( R) are ture and ( R) is the CORRECT EXPLANATION of (A) |
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| 43. |
One kilogram molecule of a gas at 400 K expands isothermally until its volume is doubled. Find the amount of work done and heat produced. Given R = 8.3 xx 10^(-3) J ( kg mole )^(-1) K^(-1). |
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| 44. |
Forces of 2N and 2sqrt2N are acting at an angle of 135^(@) to each other . The angle made by the resultant with 2sqrt2Nforce is |
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| 45. |
Nineidentical conducting rods are arranged as shown in the figure. The ends A and B are maintained at temperatues T_(1) and T_(2). Calculate the ratio of rate of flow of heat across AD to that of EB in the given arrangement in steady state. |
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| 46. |
Which of the following pair do not have same dimension? |
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Answer» PRESSURE - stress Force `=M^(1)L^(1)T^(-2)` Impulse of force =Ft `=M^(1)L^(1)T^(-2)xxT^(1)` `=M^(1)L^(1)T^(-2)` |
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| 47. |
A block of mass m is suspended from the ceilling using a string C. Another piece of string D is fitted to the other end of block. When the string D is pulled suddenly, it snaps . But when D is pulled slowly. The string C snaps. Explain. |
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Answer» Solution :Application of a sudden pull (T) on string D does not disturb the block due to its inertia. Extension of thestring C is negligible as the block PRACTICALLY REMAINS at the same place. In this case only the weight W acts on C and the string does not snap. On the other string does not snap. on the other hand, the force T may be sufficient for D to snap. But when string D is SLOWLY pulled, the applied force acts on the WHOLE SYSTEM. So, the tension T. on the string D becomes less than the tensionT. + W on C as the block also starts coming down. the tension, being higher, causes the string C to snap. 
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| 48. |
A car moves up as hill of incline 1 in 50 with a velocity of 15 KMPH. The resistance due to friction is (1)/(25)th of weight of the car. The speed of the car while moving down hill using same power is |
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Answer» 15 KMPH |
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| 49. |
A bimetallic strip is made of aluminium and steel (alpha_(Al)gtalpha_("steel")). On heating, the strip will |
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Answer» remain straight. 
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| 50. |
The correct curve between log_(e)R and log_(e)(theta-theta_(0)) is |
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