Basic Physics Questions and Answers

A particle moves in a circular path of radius R such that its speed v varies with distance x as v a x where a is a positive constant The acceleration of the particle after traversing a distance 2 R is 1 a 3 8 a 2 3 2 a 2 4 5 20 a

3 He has given me a novel 4 I promised him a reward 5 I taught him a lesson

Three objects A a solid sphere B a thin circular disk and C a circular ring each have the same mass M and radius R They all spin with the same angular speed o about their own symmetry axes The amounts of work W required to bring them to rest would satisfy the relation 1 WC WB WA 3 WB WA WC 2 WA WB Wc 4 WA WC WB

Four bodies A B C and D are projected from the ground with same speed at angles 39 43 52 and 46 with the horizontal respectively The correct relation for their horizontal range are 1 RD RB RA RC 2 RA R R Ro 3 RD RB RA Rc 4 R D

6 The moment of the force F 41 51 6k at 2 0 3 about the point 2 2 2 is given by 1 81 41 7k 2 41 1 8k 3 71 81 4k 4 71 41 8k

ample 4 Two forces are such that the sum of their magnitudes is 18 N and their resultant is perpendicular to the smaller force and magnitude of resultant is 12 Then the mag nitudes of the forces are A 12 N 6N C 10 N 8 N B 13 N 5N D 16 N 2N 0

11 Choose the correct option 1 1 AU 9 46 x 1015 m 2 1 A 10 8 cm 3 1 ly 3 26 Parsec 4 1 Parsec 1 496 10 1 m 12 The weakest fundamental force is 1 Strong nuclear force 2 Weak nuclear force 3 Electromagnetic force 4 Gravitational force 13 The parallax of a far off star as measured from two diametric extremes on the equator of the earth is 1 minute of arc If radius of earth is 6400 km then the distance of the star from the earth is 1 44 x 106 km 3 11 x 106 km 2 22 x 106 km 4 33 x 106 km 14 If the dimensions of a physical quantity are given by Ma Lb Tc then the physical quantity will be 1 Work if a 1 b 1 c 2 2 Time if a 0 b 1 c 1 3 Surface tension if a 1 b 0 c 2 4 Velocity if a 0 b 1 c 1 15 If force F velocity V and time 7 are taken as fundamental quantities the dimensional formula for energy will be 1 F V T 3 F VT 16 Zero error in an instrument introduces 1 Random error 2 Personal error 3 Least count error 4 Systematic error 17 If a number 4 732615 is to be 2 FVT 4 F V T 1 4 732 3 4 733 unded off up to three significant figures then the new number will be 20 If the units of mass length and time each are doubled then the unit of velocity will be 2 4 73 4 4 7 18 Which of the following is not the unit of time 1 Shake 2 Barn 4 Second 3 Year 19 The diameter of a cup is measured using a vernier caliper The 20 vernier scale divisions are equal to 18 main scale divisions If one division of main scale is x mm then least count of the instrument is x 21 The least count of a stopwatch is 0 2 s the time of 100 oscillations is found to be 200 s percentage error in the The maximum measurement of time is 1 10 3 0 2 22 1 Doubled 2 Halved 3 Tripled 4 Remains same For a systematic error which of the following graph is correct 2 24 Error Raka Error Error Error dical I JEF No of observations 23 An object travels 20 m in 4 s and then another 20 m in next 10 s then choose the correct option 7 2 0 1 4 5 No of observations m s No of observations 1 Average velocity for entire journey must be 20 No of observations m s 2 Average speed for entire journey must be 20 7 15 3 Average velocity for entire journey must be zero 4 Average speed for entire journey must be zero The distance travelled by an object star from rest and moving with an accel m s in the 3rd second is 15

3 Open end mercury manometer is connected to a gas chamber containing gas at a pressure of 1 38 bar The barometric pressure is 750 mm Hg Mercury level in the arm connected to gas chamber stands at 11 3 cm What is the reading in open arm of the manometer

er circuit is set up as shown The potential gradient across the potentiometer wire is k volt cm and the ammeter present in the circuit reads 1 0 A when two way key is switched off The balance points when the key between the terminals i 1 and 2 ii 1 and 3 is plugged in are found to be at lengths cm and cm respectively The magnitudes of the resistors R and X in ohms are then equal respectively to 1 W LO A 1 ke and kl R 3 X B G 2 k l and kl

The absolute temperature of air in a region linearly increases from T and T in a spac of width d Find the time taken by sound wave to goes through the region in terms of T T d the speed of sound at 273 K is V A NARAYGROUP T 273 T D 2 4 7 273 T

A block of mass 1 kg is placed on a fixed wedge at a height of 2 m as shown in figure Find maximum compression in the spring of spring constant k 50 N when the block is set free from the position 2 m 1 kg 0 2 37 2m k www 0 5

27 3 2n s 4 3 s A particle of mass 10 g is undergoing SHM of amplitude 10 cm and period 0 1 s The maximum value of force on particle is about 1 5 6 N 2 2 75 N 3 3 5 N

a A 15 kg brick is moves along an x axis Its acceleration as a function of its position is shown in figure The scale of the figure s vertical axis is set by a 24m s What is the net work performed on the brick by the force causing the acceleration eration as the brick moves from x 0 to x 8 0 m a m s 4 x m b Figure gives spring force F versus position x for the spring block arrangement of figure The scale is set by F 160 0N We release the block at x 12 cm How much work does the spring do on the block when the block moves from x 8 0cm to a x 5 0 cm b x 5 0 cm c x 8 0 cm and d x 10 0 cm 2 Fx F 1 0 3 6 8 1 x c 2 10

A chain is held on a frictionless table wi th 1 5th of its lengt h hanging over the edge If the chain h as a length L and m ass M how much w ork is required to sl owly pull the hangin g part back on the t

When a battery is connected across a series combination of inductance L and resistance R the variation in current with time tis best represented by Only one correct answer B K h 2

Velocity v versus time t graph of a particle moving in tan o tan then average speed of the particle till the time its velocity becomes zero is v m s a straight line is shown in the figure If 2 m s 1 B t s 2

23 For a particle executing simple harmonic motion the amplitude is A and time period is T The maximum speed will be 1 4AT 24 3 2 A 2A 2 24 4 2A T

Innumerable physical phenomena happening around us can be understood A only with the help of a large number of complex physical laws B only by building mathematical models C using only a small number of basic laws D only by designing experiments

4 The maximum possible efficiency of a hea engine is 1 100 T 2 2 1 T 4 Dependent upon the temperature of source 7 and sink T and is equal to 1 7

amped Harmonic Motion 29 The quality factor of a sonometer wire is 4 000 The wire vibrates at a frequency of 300 Hz Find the time in which the amplitude decreases to half of its initial value 20 2 4000 4 24 s

A body of mass 30 kg stands on a weighing machine lying on the floor of a lift What will be the weight of the body when i lift moves upwards with an acceleration 2 2 ms 2 ii lift moves downward with an acceleration 2 2 ms and iii lift falls freely Given g 9 8 ms2

The value of the Plank constant we measure here h 6 4 0 2 x 10 34 J sec is in agreement with the standard measured value 6 62607004 10 4 J sec The large error here are due to effect of O the reverse photo currents O temperature variation O all of the above O the broad wavelength width of the filters

Three particles of masses 1 kg 2 kg and 3 kg are placed at three corners of a right angled triangle of sides 3 cm 4 cm and 5 cm as shown in the figure The centre of mass from 1 kg mass is y axis 3 cm 0 0 3 kg 4 cm 1 kg O 1 33 cm 1 5 cm 2 cm 1 cm 2 kg 1 14 cm 1 5 cm 1 7 cm 0 9 cm x axis

7 Two identical springs have the same force constant 73 5 Nm The elongation produced in each spring in three cases shown in Figure 1 Figure 2 and Figure 3 are g 9 8 ms wwwwwww wwwwwwww 5 kg Figure 1 m 00000 5 kg Figure 2 4 m 1 3 5 kg Figure 3 1 3 22 TE SI y ph 1 3 23 Fo th m 1

Energy band gap of silicon is 1 14 eV 19 f Maximum wavelength at which silicon will start showing conductivity is 1 10888 nm 3 108 88 nm Mo 2 1088 8 nm 4 10 888 nm 20 1 14 eV for fufce cal 1 10888 nm 3 108 88 nm 2 108 4 10 frica Mobility

carpet is laid on the floor having mass per unit length A External force required to move one end of the carpet with uniform velocity Vo as shown in figure is 77 O2AV2 O AV2 O XV2 2 11 2 V

Five capacitors are connected as show n in the figure Initially all capacitors ar e uncharged and S is open When S is c losed then the potential difference bet ween points M and N is assume steady state to be achieved af ter S closes sir please solve it by Kirchoofs current I aw not by KCL 7v S 6 F 4 F N 2 F 4 F HE 1 2uF 31v

A particle travels in circle of radius 20 cm at a speed that uniformly increases It speed changes from 5 m s to 6 m s in 2 s The angular acceleration is 2 rad s 2 2 5 rad s 5 rad s 2 1 5 rad s 2

The block A in figure weighs 100 N The coefficient of static friction between the block and the table is 0 25 The weight of the block B is maximum for the system to be in equilibrium The value of T is T QUX T T A B imunin 45

Calculate the hinge force when the rod of mass M becomes vertical Initial situation is shown in figure and string is then cut hinge is frictionless wym O Fx 0 Fy y Mg O Fx Mg Fy Mg O Fx Mg Fy Mg O Fx 0 Fy Mg L 8

Question 19 M M 4 00 N M 1 00 At a point P on the screen at distance D from the slits in standard YDSE experiment 3rdmaxima is observed at t 0 Now screen is slowly moved with constant speed away from the slits in such a way that the centre of slits and centre of screen always lie on same line and at t 1 sec the intensity at point P is observed to be 3 of 4 maximum intensity in between 2nd and 3rd maxima The speed of screen can be Correct Answer

A sphere of radius 0 5 m rolls on the plank without slipping If velocity of sphere and plank is 10 m s and 5 m s respectively as shown then angular velocity of sphere is O Options 30 rad s 10 rad s X 20 rad s 15 rad s 10 m s 5 m s

Mark the correct statement about longitudinal pressure wave A The density variation and the longitudinal velocity of the particles have their maxima and minima at the position of equilibrium of the particles B At the position of maximum displacement the density is at the ambient environment value C Greatest compression occurs at the same time and place where the velocity of the particles is maximum and in direction of wave propagation D Greatest rarefraction occurs at the same time and place where the velocity of the particles is maximum and in direction of wave propagation

Derive the e m f equation of a D C generator An 8 pole DC generator has 500 armature conductors and a useful flux of 0 5wb What will be the EMF generated if it is lap connected and runs at 1200 RPM what must be the speed at which it is to be driven to produce the same EMF if it is wave wound

In a Rutherford a scattering experiment when 1 a projectile of charge Z and mass M approaches a target nucleus of charge Z and mass M the distance of closest approach is r The energy of the projectile is 1 directly proportional to M M 2 directly proportional to ZZ 3 directly proportional to Z 4 directly proportional to mass M a Z 3 4 2 M Fr 1 M x M HIS 2 t M THIS h

A man can swim with a speed of 3m s in still water and river flows at the rate of 5m s River width is 500m 4 A For shortest path journey 0 Tan 3 B For shortest path journery 0 Tan 3 17 C time taken for shortest path journey is 3 36 min 28 D time taken to cross river in shortest time is 2 min 36 Direction of swimming

A weight W rests on the bar AB as shown in figure The cable connecting W B passes over frictionless pulley If bar AB has negligible weight find reaction at A for system to be in equilibrium O O O W L a L a W L a L a W L 2a L a B W

A source emits sound uniformly in all directions A radial line is drawn from this source On this lir determine the positions of two points 1 00 m apart such that the intensity level at one point is 2 C Db greater than the intensity level at the other

I 10 1 The image of a point source kept at origin O forms at point A due to transparent sphere of radius 10 cm as shown in the figure Here OX is the optical axis of the sphere Now the sphere is t cut into two equal parts along a plane perpendicular to the horizontal axis OX and the plane surface of the left half PRCS is silvered The right half PQSC is removed Now the co ordinate of image of point source O formed by remaining silvered hemisphere will be A 10 cm 0 C 30 cm 0 I 1 40 cm B 20 cm 0 D 40 cm 01 R I I I 10 cm A

A small ball of mass m starts at a point A with speed vand moves along a frictionless track AB as shown The track BC has coefficient of friction The ball comes to stop at C after travelling a distance L which is h v A h v 2 2 g NA 2 g hvo 2 g 2h v C 2 g B D A B L 2

sin x x x 5 2 7 If f x 5 b 1 ab x 11x 24 a a x 3 x 5 a b e R then denotes the greatest integer function 25 b 6 5 108 c a b x 5 is continuous at 25 36 H x 5 6 b a b 13 d a 17 29 23 b 100 1 0 6 5

A ball projected from ground at an angle of 45 just clears a wall and ball strikes the ground distance of 6m on the other side of the wall the height of the wall is A 4 4 m C 3 6 m B 2 4 m D 1 6 m 20

A light ray parallel to the x axis strikes the outer reflecting surface of a sphere at a point 2 2 0 Centre of sphere is at the point 0 0 1 The unit vector along the direction of the reflected ray is xi y zk Find the value of yz 8x

An electron accelerated by a potential difference V 3 6 V first enters a region of uniform electric field of a parallel plate capacitor whose plates extend over a length 6 cm in the direction of initial velocity The electric field is normal to the direction of initial velocity as shown in figure and its strength varies with time as E ax t where a 3200 Vm s Then the electron enters a region of uniform magnetic field of induction B x10T Direction of magnetic field is same as that of the electric field Mass of electron m 9 x 10 31 kg e 1 6 10 1 C Neglect the effect of induced magnetic field e m Vor HIL B Path followed by the electron while moving in electric field is parabolic Path followed by the electron while moving in magnetic field is helical Pitch of holical path of ploctran is 9 mm

Blocks of mass M and M are connected by a cord which passes over the pulleys P and P2 as shown in the figure If there is no friction the acceleration of the block of mass M will be O M 9 4M M M LABEL178 M P 4

In the circuit shown in the figure the symbols have their usual meaning only one of the three switches is kept closed and other two are open during the entire experiment The value of resistance is R 20 2 When the angular frequency o of the 100 V source is adjusted to 500 rad s 1000 rad s and 2000 rad s it was found that the current was 4A 5A and 4A respectively R www A The switch that was closed is S B The switch that was closed is S C The value of L is 10 mH D The value of C is 100 F S S21 S3 100 V L C 16 roooo mm C L

When water freezes it expands about nine percent What would be the pressure increase inside your automobile engine block assumed to be rigid if the water in there froze The bulk modulus of ice is 2 0x109 Pa and 1 atm 1 0 105 Pa 18 atm 3 1800 atm C 1080 atm 5 270 atm

In given figure the small block of mass 2 m is released from rest when the string is in horizontal position Smooth rod m 2gl 4 gl mg string Maximum possible velocity of ring of mass m is Assuming zero friction 2m fhm

velocities of different molecules cancel each other A At constant volume on increasing temperature the collision frequency increases R Collision frequency temperature of gas

Q 1 Solve the following Draw a graph showing the variation of electron energy levels of Silicon as a function of its interatomic distance Explain from it why Silicon is a insulator at OK and semiconductor at RT