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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 15001. |
A scientist says that the efficiency of his heal engine which operates at source temperature 127^@Cand sink temperature 27^@Cis 26%, then |
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Answer» It is impossible |
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| 15002. |
List - I (a) Centrifugal force (b) Centripetal force (c) Tangential force (d) Angular velocity List - II (e) Along the axis of rotation (f) Towards the centre of rotation (g) Away from the centre of rotation (h) Changes the angular velocity |
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Answer» `a-h,B-g,c-f,d-e` |
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| 15003. |
What is the effect of pressures on boiling point of water ? |
| Answer» SOLUTION :Boiling point of water BECOMES HIGH. | |
| 15004. |
A thin uniformmetallic rod of length0.5 m andradius 0.1 m rotates with an angular velocity 400 rad/s in a horizontal plane about a vertical axis passsing throughone of its ends. Calculate tension in the rod and the elongation of the rod. The density of materialof the rod is 10^(4)kg//m^(3) and Young.s modulus is 2xx10^(11)N //m^(2). |
Answer» Solution : (a) Consideran element of lengthdr at a distance .r.from the AXIS of rotation as shown in fig. The CENTRIPETAL forceacting on this ELEMENTWILL be `dT =dm r omega^(2) =(rho A dr) r omega^(2)` As this force is providedby tension in the rod (due to elasticity), so the tension in the rod at a distance from the axis of rotation due to all elementsbetween x = r to x = L. centripetal force due to all elementsbetweenx = r to x = L. i.e., `T=int_(r)^(L) rhoA omega^(2) r dr=(1)/(2) rhoAomega^(2)[L^(2)-r^(2)] ......(1)` So here `T=(1)/(2) XX 10^(4) xx pi xx 10^(-2) xx (400)^(2) [((1)/(2))^(2) -r^(2)]` `=8pi xx 10^(6) [(1)/(4) -r^(2)]N` `T=(1)/(2) rho A omega^(2) (L^(2)-r^(2))` elongationof small element `de =(rho A omega^(2))/( 2Ay) (L^(2)-r^(2)) dr`, Total ELONGATION `e=intde=(rho omega^(2))/(2y) int_(O)^(L)(L^(2)-r^(2))dr=(rho^(2) omega^(2)L^(3))/(3y)` |
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| 15006. |
Maximum and minimum magnitudes of the resultant of two vectors of magnitudes P and Q are found to be in the ratio 3:1, Which of the following relations is true ? |
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Answer» <P>P = Q |
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| 15007. |
Define coefficient of Volume expansion ?Give its unit. |
| Answer» SOLUTION :The coefficient of Volume expansion of a substance is defined as the increase in volume PER unit original volume per DEGREE rise in its temperature. The unit of `alpha_(V) " is "^(@)C^(-1) (or) K^(-1)` | |
| 15008. |
The difference in properties of a substance in three states of matter depends on |
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Answer» DIFFERENCE in molecular shape |
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| 15009. |
A train is moving with a unifrom speed of 33 m/ s and an observer is approaching the train with the same speed. If the train blows a whistle of frequency 1000 Hz and the velocity of sound is 333 m/s, then the apparent frequency of the sound that the observer hear is |
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Answer» 1220 Hz Velocity of the observer, `u_(0)=33 m//s)` Now, velocity of sound, V = 333 m/s As the source and the observer are approching each other, so , APPARENT frequency, `n.=(v+u_(0))/(v-u_(2)) cdot n =(333+33)/(333-333)xx1000 = 1220 ` HzThe option (A) is correct. |
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| 15010. |
Which of the following is a unit of distance? |
| Answer» Solution :Light year | |
| 15011. |
When a body slides down from rest along a smooth inclined plane making an angle of 45^(@) with the horizontal, it takes time T. When the same body slides down from rest along a rough inclined plane making the same angle and through the same distance, it is seen to take time pT, where p is some number greater than 1. Calculate the coefficient of friction between the body and the rough plane. |
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Answer» Solution :When slopeis smoothas shownin figureboydslidesonslope `F = ma` `F= mg SIN theta ` `a= g sin theta ` `theta= 45^(@)`  `a= g (1)/(SQRT(2))` Letdistancecovered by bodybe dd =mt + `(1)/(2 ) at^(2)` ` d= (1)/(2) ( g)/(sqrt(2))t^(2)` `d= (gt^(2))/(2sqrt(2))` Heret = pt d= - (p T ) `+(1)/(2) ` a(p T ) COMPARING (1) and (2) `(1-mu ) p^(2) =1` `1-mu = (1)/( p^(2))` `mu= 1= (1)/(p^(2))` |
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| 15012. |
An ideal triatomic gas expands according to law PV^2= constant. If molar heat capacity of the gas forthe process is NR, then N is equal to |
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Answer» |
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| 15013. |
A racing car is travelling along a track at a constant speed of 40 m/s. A T.V. camera men is recording the event from a distance of 30 m directly away from the track as shown in figure. In order to keep the car under view in the positio shown, the angular speed with which the camera should be rotated, is- |
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Answer» `4//3 RAD //SEC` |
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| 15014. |
(A) : A helicopter must necessarity have two propellers. (R) : Two propellers are provide in helocopter in order to conserve inear momentum. |
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Answer» Both 'A' and 'R' are TRUE 'R' is the CORRECT EXPLANATION of 'A' |
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| 15015. |
In the pulley system shown in figure . P and Q are fixed pulleys while A, B and C are movable pulleys each of mass 1kg . Thestrings are vertical and inextensible . Find the tension in the string and acceleration of frictionless pulleys A,B and C |
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Answer» Solution :A single string whose ends are tied to centres of A and B, passes over all the pulleys, so tension at each point of string is same equal to T WEIGHT of each pulley A,B andC is `mg=1g `Newton. Let `y_(A),y_(B)` and y_(C)`be the distance of centres of pulleys A,B and Cfrom fixed pulleys at any time t. Following the string STARTING from end A and reaching upto end B, we have `(y_(B)-y_(A))+y_(B) +2y_(A)+y_(C)+y_(C)-y_(B)=L`= constant Differentitating twice with respect to t, we get `(d^(2)y_(A))/(dt^(2))+(d^(2)y_(B))/(dt^(2))+2(d^(2)y_(C))/(dt^(2))=0` i.e., `a_(A)+a_(B)+2a_(C)=0` where `a_(A),a_(B)`, and `a_(C)` are acceleration of pulleys A,B,C respectively. Now equations of MOTION of pulleys A,B and C are `mg+T-2T=ma_(A) rArr mg-T=ma_(A)`....(2) `mg+T-2T=ma_(B) rArr mg-T=ma_(B)`....(3) and `mg-2T=ma_(C)`....(4) From (2) and(3) it is obvious that and `a_(A)=a_(B) =(g-T/M) `.....(5) and from (4), `a_(C) =g-(2T)/m`.....(6) substituting `a_(A),a_(B)` and `a_(C) ` in (1) , we get (g-T/m)+(g-T/m)+2(g-(2T)/m)=0` `4g-(6T)/m=0 rArr T=2/3 mg=2/3xx1xx9.8=6.5N` `:. a_(A)=a_(B)=(g-T/m)=9.8-(6.5)/1=3.3 m//s^(2)` From (1), `ac=-a_(A)= -3.3m//s^(2)` |
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| 15016. |
For the above problem, the direction of the gravitational intensity at any arbitary point P is indicated by the arrow (i) d, (ii)e, (iii) f, (iv) g. |
| Answer» Solution :As per explanation given in the ANSWER of `Q. 10`, the DIRECTION of gravitational intensity at `P` will be along e.i.e., the option (ii) is correct. | |
| 15017. |
An inverted u-tube has its two limbs in water and kerosene contained in two beakers. If water rises to a height of 10em, to whar height does kerosene (density=0.8gmice) rise in the other limb? |
| Answer» Answer :B | |
| 15018. |
A particle moving in a circular path has an angular momentum of L. If the frequency of rotation is halved, then its angular momentum becomes |
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Answer» `(L)/(2)` Now, `omega'=omega//2` Hence, `L'=Iomega'=mr^(2)=(omega)/(2)=PIMR^(2)f RARR (L)/(L')=(2M pi r^(2)f)/(pi mr^(2)f)rArr L'=(L)/(2)`. |
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| 15019. |
If a block of mass m lying on a frictionless inclined plane of length L height h and angle ofinclinationtheta, then the velocity at its bottom is |
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Answer» `g sin THETA ` |
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| 15020. |
If a block of mass m lying on a frictionless inclined plane of length L height h and angle ofinclinationtheta, then the time taken to reach thebottom is |
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Answer» `G sin theta ` |
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| 15021. |
A calorimeter contains 10kg of water and some ice. Variation of temperature with time, when the calorimeter is heated over a slow burner is as follows. Ignoring heat absurbed by calorimeter, The amount of ice present is (0.16 xx n)kg. Find the .n.. |
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| 15022. |
The potential energy of a simple harmonic oscillator when the particle is half way to its end point is……….(where E is total (mechanical) energy) |
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Answer» `(1)/(2)E` POTENTIAL energy `= (1)/(2)m omega^(2) y^(2)` `=(1)/(2)m omega^(2) (A/2)^(2) = (E )/(4)`. |
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| 15023. |
A molecule of mass m of an ideal gas collides with the wall of a vessel with a velocity v and returns back with the same velocity. The change in the linear momentum of the molecule is |
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Answer» 2mv |
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| 15024. |
Two chambers, one containing m_(1)g of a gas at P_(1) pressure and other containing m_(1)g of a gas at P_(2) pressure are put in communication with each other. If temperature remains constant, the common pressure reached will be |
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Answer» SOLUTION :According to Boyle.s law `(P)/(rho)` = cons tan t `therefore V_(1) = (m_(1))/(P_(1)) = (km_(1))/(P_(1)) and V_(2) = (km_(2))/(P_(2)) ` Total VOLUME = K `((m_(1))/(P_(1)) + (m_(2))/(P_(2)) ) ` LET mixture has common pressure P and common density `rho`. `rho = ((m_(1) + m_(2)))/(k ((m_(1))/(P_(1)) + (m_(2))/(P_(2)) ) ) rArr P = k rho = ( (m_(1) + m_(2))/((m_(1))/(P_(1)) + (m_(2))/(P_(2)) ))t = (P_(1) P_(2) (m_(1) + m_(2)) )/((P_(2) m_(1) + m_(2) P_(1) ) ) ` |
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| 15025. |
Consider the process on a system shown in figure. During the process, the work done by the system |
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Answer» CONTINUOUSLY INCREASES |
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| 15026. |
One of the domains of physics “ microscopic" Deals with the phenomena atI) atomic- level II) molecular- level III) nuclear -leve |
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Answer» Only I and III are CORRECT |
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| 15027. |
Give the expression for the energy evolved, when the surface area of the liquid is decreased. |
| Answer» Solution :Energy EVOLVED (SURFACE TENSION) (decrease in the surface area). | |
| 15028. |
In car lift compressed air exerts a force F_1 on a small piston having a radius of 5 cm. This pressure is transmitted to a second piston of radius 15 cm. If the mass of the car to be lifted is 1350 kg, what is F_1 ? What is the pressure necessary to ac complish this task ? |
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Answer» SOLUTION :`(F_(1))/(A_(1))=(F_(2))/(A_(2))` `F_(1)=F_(2)(A_(1))/(A_(2)) = F_(2)((pir_(1)^(2))/(pir_(2)^(2)))` `F_(1)= 1350xx9.8((5XX10^(-2))/(15xx10^(2)))^(2)` =1470 N. |
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| 15029. |
The total work done on a particle is equal to the change in its kinetic energy |
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Answer» always |
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| 15031. |
The temperature at which oxygen molecules have the same root mean square speed as that of hydrogen molecules at 300K is |
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Answer» 600K |
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| 15032. |
Which of the following functions of time represent (a) simple harmonic, (b) periodic but not simple harmonic, and (c) non-periodic motion? Give period for each case ofperiodic motion (w is any positive constant): (a) sin omega t - cos omega t (b) sin^(3) omega t (c) 3 cos (pi//4 - 2 omega t) (d) cos omega t + cos 3 omega t + cos 5 omega t (e) "exp" (-omega^(2)t^(2)) (f) 1+ omega t + omega^(2)t^(2). |
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Answer» Solution :The function will represent a periodic motion,if it is identically repeated after a fixed interval of time and will represent S.H.M. if it can be written uniquely in the form of a cos `((2pi t)/(T)+phi)` or ` sin ((2pi t)/(T)+phi)`, where T is the time period. (a) `sin omega t - cos omega t = sqrt(2) [(1)/(sqrt(2)) sin omega t -(1)/(sqrt(2)) cos omega t]` `=sqrt(2) [sin omega t cos.(pi)/(4)-cos omega t sin.(pi)/(4)]` `= sqrt(2) sin (omega t-(pi)/(4))` It is a S.H.M and its period is `2pi//omega` (B) `sin^(3) omega t = (1)/(3) [3 sin omega t - sin omega t]` Here each TERMS `sin omega t` and `sin 3 omega t` individually represents S.H.M But (ii) which is the outcome of the superposition of two SHMs will only be periodic but not SHMs. Its time period is `2pi//omega`. (c) `3 cos ((pi)/(4)-2 omega t) = 3 cos (2 omega t -(pi)/(4)) [:' cos (-theta) = cos theta]` Clearly it represents SHM and its time period is `2pi//2omega`. (d) `cos omega t + cos 3 omega t +cos 5 omega t`. It is represents the periodic but no S.H.M Its time period is `2pi//omega` (E) `e^(-w2t2)`. It is an exponential function which never repeats itself. Therefore it represents non-periodic motion. (f) `1 + wt +w^(2)t^(2)` also represents non periodic motion. |
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| 15033. |
What is meant conservative force? |
| Answer» SOLUTION :A force is said to be a conservative force if the work done by or against the force in moving the body DEPENDS only on the initial and FINAL positions of the body and not on the NATURE of the PATH followed between the initial and final positions. | |
| 15034. |
Skidding occurs when the maximum frictional force of a flat road on a car is |
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Answer» LESS than CENTRIPETAL force required |
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| 15035. |
A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registered at 140°F. What is the fall in temperature as registered by the centigrade thermometer ? |
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Answer» `80^(@)` |
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| 15036. |
A child is standing with folded hands at the centre of a platform rotating about its central axis. The K.E. of the system is K. The child now stretches his arms so that M.I. of the system doubles. The K.E.Of the system now is |
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Answer» 2K |
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| 15037. |
A man walks east with certain velocity. A car is travelling along a road which is 30^(@) West of North. While a bus is travelling in another road which is 60^(@)South of West. Find the angle between velocity vector of (a) man and car (b) car and bus ( c) bus and man. |
Answer» Solution : From the diagram the angle between VELOCITY VECTOR of MAN and car is `90^(@)+30^(@)=120^(@)` The angle between velocity vector of car and bus is `60^(@)+60^(@)=120^(@)` The angle between velocity of bus and man is `30^(@)+90^(@)=120^(@)` |
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| 15038. |
The centre of mass of the system of particles depends on(a) masses of the particles(b) relative position of the particles |
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Answer» Only a is TRUE |
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| 15039. |
The correct value of 0^(@)C on the Kelvin scale is …………….. |
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Answer» 273.15 K |
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| 15040. |
A vertical cylinder with heat- conducting walls is closed at the bottom and is fitted with a smooth light piston. It contains one mole of an ideal gas. The temperature of the gas is always equal to the surrounding 's temperature, T_0 The piston is moved up slowly to increase the volume of the gas to eta times. Which of the following is incorrect? |
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Answer» Work done by the gas is `RT_(0)` In `eta`. |
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| 15041. |
Two particles mass 100 g and 300 g at a given time have velocities 10 hati-7hatj-3hatk and 7hati-9hatj+6hatk ms^(-1) respectively. Detegnine yelocity of center of mass. |
| Answer» Solution :VELOCITY of center of MASS`=(31i-34j+15k)/(2)ms^(-1)` | |
| 15042. |
A ball is projected from point O on the ground. It hits a smooth vertical wall AB at a height h and rebounds elastically. The ball finally lands at a point C on the ground. During the course of motion, the maximum height attained by the ball is H. (a) Find the ratio (h)/(H) if (OA)/(OC) = (1)/(3) (b)Find the magnitude of average acceleration of the projectile for its entire course of flight if it was projected at an angle of 45^(@) to the horizontal. |
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Answer» |
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| 15043. |
ABC is a right angles triangle, right angled at C. Two particles start from A and C. along AC and CB respectively with uniform velocities u and v. The shortest distance between them is (AC=L) |
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Answer» `(Lv)/(sqrt(v^(2)+U^(2)))` |
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| 15044. |
When 5 moles of an ideal gas is compressed isothermally, its volume decreases from 5 litre to 1 litre. If the gas is at 27^(@)C, find the work done on the gas. |
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Answer» Solution :In the case of .n. MOLES, work done on the gas `W=nRT log_(e ) ((V_(2))/(V_(1)))=nRT xx 2.30 26 xxlog_(10)((V_(2))/(V_(1)))` `R=8.314"J mole"^(-1)K^(-1)`, `T=27+273=300K, V_(1)=1` litre`=10^(-3)m^(3)` `:.V_(2)=5`litre`=5xx10^(-3)m^(3) rArr (V_(2))/(V_(1)) =(1)/(5)` `:.W=5xx8.314 xx 300xx2.3026xx log_(10)((1)/(5))` `=5xx8.314 xx300xx2.3026xx(-0.6990)= -2.007xx10^(4)J` |
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| 15045. |
(A) : An ice block with lead shot is floating in water. When ice melt completely water level slightly drops. (R ) : When ice block with lead shot is placed in water, volume of displaced water is more than that of the ice block. |
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Answer» Both (A) and (R ) are TRUE and (R ) is the correct explanation of (A) |
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| 15046. |
Draw the x to tgraphs for positive, negative and zero acceleration. |
Answer» Solution :The average ACCELERATION EQUALS the CONSTANT value of acceleration during the interval. If the velocity of an OBJECT is `v_(0)`at t = 0 and v at TIME t, 
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| 15047. |
A force of 1 Nacts on a 1kg mass at rest for 1 s. In another case IN force acts on 1kg mass at rest and moves it through lm. The ratio of kinetic energies in the two cases is |
| Answer» ANSWER :B | |
| 15048. |
The magnitude of gravitational potential energy at a distance r from the centre of earth is U, then show the weight at this point in the form of U. |
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Answer» Solution :`U=(Gm_em)/R=((Gm_e)/r^2)MR = gmr ` `:. mg =U/r` |
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| 15049. |
Which of the following potential energy curves in Fig. 6. 18 cannot describe the elastic collision of two billiard balls? Here r is the distance between centres of the balls. |
| Answer» SOLUTION :All EXCEPT (V) are IMPOSSIBLE. | |
| 15050. |
The radii of two spheres of same material are Im and 4m, their temper-atures are 4000K and 2000K respectively. The ratio of amounts of heat emitted by them in a given time interval will be |
| Answer» ANSWER :C | |