Basic Physics Questions and Answers

35 The energy of a photon is E hv and the momentum of photon is P then the velocity of photon will be 26 3 wha Whiel 2 EP 4

A thin uniform spherical shell of mass m 2 kg and radius R 10 cm is placed on a rough horizontal surface with a coefficient of friction 0 4 A horizontal force F is applied to the spherical shell at a height R 3 above the centre as shown The maximum magnitude of the applied force F for which the spherical shell will be rolling without slipping is take g 10 m s A 20 N C 40 N B 30 N D 60 N R 3 F H 0 4 m R

1 A body is moving with variable acceleration a along a straight line The average acceleration of body in time interval t to t is 2 1 a t t 2 ja dt 3 t 1 a t t 2 4 a dt t t

3 A force F b Vi XN b is a constant acts on a particle as it undergoes counter clockwise x y circular motion in a circle x y 16 The work done by the force when the particle undergoes one complete revolution is x y are in m A Zero C 2 bJ B 2n bJ D None of these

A block of mass 2 kg is kept on a truck moving with a constant acceleration The height h of the block is 60 cm and its width w is 15 cm The surface between the block and the truck is sufficiently rough to prevent slipping The minimum acceleration of the truck at 77 which the block will topple is take g 10 m s A 2 5 m s C 4 5 m s B 3 5 m s D 5 5 m s

Problem 4 4 A load cell Fig 4 40 is formed of a hollow steel cylinder loaded axially The four strain gauges are so connected as to enhance the signal and compensate for temperature variation The load cell has a cross sectional area of 2 cm Young s modulus of steel is 2 07 x 10 N m and Poisson s ratio 0 3 Strain gauge resistance 1000 2 I Gauge factor 2 1 310 RR R R A E R R Ra innan R R

A conical container of radius R 1m and height H 5m is filled completely with liquid There is a hole at the bottom of container of area 10 3 m2 see figure Time taken to empty the conical container in sec is 100T Find the value of T

34 A ball is thrown vertically down from a certain height with some speed After rebound with ground it is caught at the same point with same speed at which it was thrown Its velocity time v t graph Taking vertically downward direction as positive is best represented by V L 1 2 3 4 0 V t

Choose incorrect statement about electric field lines due to a charge configuration The density of field lines at a point represents proportional strength of electric field at that point They are lines or curves which emerge from O positive charge and terminate at negative charge O They can form a closed loop

A liquid is filled in a large container as shown A source S is moving with constant velocity 3v 4 in upward direction A man A is stationary on the surface of water such that his ear is in the air Another man B is moving downward inside the water with constant velocity v 3 Source emits sound of frequency f Speed of sound in the air is v and in the liquid is 5v Then A Wave length received by man A is 7v 4f 35v 4f B Wave length received by man B is 2f C Frequency received by man A is 7 8f 15 D Frequency received by man B is 3v 4 S A Source

If n 1 is taken to be reference of the potential energy what will be the kinetic energy in eV of an electro in second excited state in Li 1 13 6 eV 3 54 4 eV 2 108 8 eV 4 12 08 eV

A radioactive sample disintegrates via two independent decay processes having half lives T and T2 respectively The effective half life T1 2 1 2 1 2 of the nuclei is 1 None of the above 2 T1 2 T T 1 2 1 2 3 T1 2 4 T1 2 1 2 1 2 T 1 1 2 T 2 1 2 T t 1 2 7 2 1 2 T T 2 1 2 1 2

A pan balance has a container of water with an overflow spout on the right hand pan as shown It is full of water right up to the overflow spout A container on the left hand pan is positioned to catch any water that overflows The entire apparatus is adjusted so that it s balanced A brass weight on the end of a string is then lowered into the water but not allowed to rest on the bottom of the container What happens next Water A Water overflows and the right side of the balance tips down B Water overflows and the left side of the balance tips down C Water overflows but the balance remains balanced

A ring of radius R is rolling without slipping over a fixed surfaces It s linear mass density varies as 1 cos0 as shown At the instant shown centre of ring has speed v Find its total kinetic energy in joule Given R 1m v 1 m s o 1 2 kg m R Q 2 2 2 cose

In Young s double slit arrangement slits are separated by a gap of 0 5 mm and the screen is placed at a distance of 0 5 m from them The distance between the first and the third bright fringe formed when the slits are illuminated by a monochromatic light of 5890 AA is 9 1 1178 10 m 2 1178 x 10 6 m 3 1178 10 2 m 4 5890 X 10 7 m

is of be of 23 The of a photocells kept fixed The wavelength of the ligh falling on the cathode is gradually changed The plate current I of photocel varies as follows MS164 a c 1776 2 b 2 2 VL d

placed vertically as shown A point charge Qo is placed at point O at a distance L from its one end Potential energy of charge Qo is equal to B L A OAQ In2 4180 OAQ In2 200 O AQ 40E0

Zero Marks in all outer In shown system strings and pulley are frictionless and massless Block A is moving downward with velocity of 7m s which is increasing at a rate of 2 m s2 while block C is moving upward with a velocity of 9 m s whi decreasing at a rate of 3 m s The block B is moving downward with velocity of v8 m s which is decreasing at a rate of as m s Find the value of Vs as A B C

Match List I with List II List I a 10 km height over earth s surface b 70 km height over earth s surface c 180 km height over earth s surface d 270 km height over earth s surface List II i Thermosphere ii Mesosphere iii Stratosphere iv Troposphere 1 a i v b i i i c i i d i 2 a i b iv c iii d ii 3 a iii b ii c i d iv 4 a ii b i c iv d iii O 1 02 3

In the circuit shown 1 and 2 are two ideal sources of unknown emfs Some currentsare shown in some branches of the circuit Potential difference across resistance 60 isVA VB 10V then 2 amp R 3 amp 452 452 81 17 252 82 www 352 3525 www 652

The time period of a simple pendulum is given by T 2 g measured value of the length of pendulum is 10 cm known to a 1 mm accuracy The time for 200 oscillations of the pendulum is found to be 100 second using a clock of 1 s resolution The percentage accuracy in the determination of g using this pendulum is x The value of x to the nearest integer is 1 2 2 3 3 5 4 4 The

An oil drop of radius 2 mm with a density 3 g cm is held stationary under a constant electric field 3 55 105 V m in 3 the Millikan s oil drop experiment What is the number of excess electrons that the oil drop will possess consider g 9 81 m s 1 48 8 10 1 2 1 73 10 0 3 17 3 1010 X 4 1 73 10 2

3 36 The resistors 40002 and 80002 are connected in series with a 6 volt battery It is desired to measure the current in the circuit An ammeter of 10 ohms resistance is used for this purpose What will be the reading in the ammeter Similarly if a voltmeter of 10 00092 resistance is used to measure the potential difference across the 40002 resistor what will be the reading in the voltmeter

In the resistor network shown in the figure all the resistors are identical and each equal to 102 A current of 1A passes from terminal a to terminal b as shown in the figure The voltage between the terminals a and b is g R 10 1 4V

Example 1 Classify each of the following reactions as combination decomposition displacement or double displacement reactions i 2 KNO3 s 2 KNO s O g ii Zn s 2 AgNO3 aq Zn NO3 2 aq 2 Ag s iii Ni NO3 aq 2 NaOH aq Ni OH 2 NaNO3 aq iv Zn s 2 HCl aq ZnCl aq H g v 2 CuO s 2 Cu s O g vi Cl g 2 NaBr aq vii MgO s C s Br 2 NaCl aq CO g Mg s viii 2 KCIO3 2 KCl s 3 0 g ix CaQ s H O Ca OH aq

Conducting shell of radius R carrying charge Q another charge Q is placed at 3R distance from centre of shell If the potential at point P due to charge on 11 KQ Then the value of 20n is 3n R shell is 5 X X X X X X R X PAN X R 2 X X X 3R o

Ith linear 1 31 A semi circular ring of mass charge density hinged at its centre is placed in a uniform electric field as shown in the figure 1 451 If the ring is slightly rotated about O and released find the time period in sec of oscillation Take m 8 kg 2 C m and E 2 N c Assume that coil is rotated in its own plane 0

You place a box of mass m 10 kg against a vertical wall You apply a constant force F to the box where F 200 N and the force is at an angle of 0 60 above the horizontal The coefficient of kinetic fric Blackboard Help n the book and the wall is 0 3 If the book is initially at rest what is its speed after it has traveled 0 5 m up the wall ALL e 3

Two sound waves of frequencies 100 Hz and 102 Hz and having same amplitude A are interfering A stationary detector which can detect waves of amplitude greater than or equal to A in a given time interval of 12 seconds find the total duration in which detector is active 8 2A Ao I I 1 1 6 s 1 4 s 1 3 s SSS cycle 2 3 sj 3 4 s 5 6 s SSS

uestion Type Single Correct A Q No 6 This section contains SIX 06 questions Each question has FOUR options ONLY ONE of these four options is the correct answer For each question choose the option corresponding to the correct answer Answer to each question will be evaluated according to the following marking scheme Full Marks 3 If ONLY the correct option is chosen Zero Marks 0 If none of the options is chosen i e the question is unanswered Negative Marks 1 In all other cases When A B AB then A and B are perpendicular to each other A and B act in the same direction Marks For Correct Answer 3 00 and act in the opposite direction Negative Mark 1 00 View In English v 0 0

49 Maurine Lewis editor of a leading publishing house estimates that it takes 11 months on average To complete the process of publishing a book from having the manuscript until finished With a standard deviation of 2 4 months He thinks that the normal distribution describes well the distribution of publication times Of 19 books that will work this year approximately how many will complete the publication process in less than a year

2 22 Two identical planar capacitor connected in parallel and charged to a voltage U 12V When you disconnect them from the voltage source the distance between the plates of one of the capacitors is reduced to one third of the original distance What will be the new voltage on the capacitors Ans 6V

9 Two short identical magnetic dipoles of magneti moments 1 Am each placed at a separation c 2 m with their axis perpendicular to each othe The resultant magnetic field at a point midwa between the dipoles is 1 5 x 10 7 T 3 10 7 T 2 5 x 10 7 T 4 5 5 x 10 7 T

1 36 A non conducting sphere of radius R 5 cm has its centre at origin O of co ordinate system shown in figure 1 453 It has a spherical cavity of radius r 1 cm whose centre is at 0 3 cm Solid material of sphere has uniform positive charge densit 10 6 C m Calculate potential at point P 4 cm 0 T p P X

3 1 Rnt 3 24 At a place on earth horizontal component of earth s magnetic field is B and B and vertical component of earth s magnetic field is B If a magnetic needle is kept in a vertical plane making an angle a with the magnetic meridian then square of time period of vibration needle in this plane is proportional to 1 B cos a 4 1 B cosa B 2 4 Rt

7 A particle having charge q and mass m is released from rest on the axis of a fixed ring of total charge Q and radius R from a distance 3R Its kinetic energy when it reaches the centre of ring is 1 3 Qq 460R Qq 2R R 3R 2 ET Qq 86R Qq 16R

Figure shows cross section view of a infinite cylindrical wire with a cylinderical cavity current density is uniform jok as shown in figure Field inside cavity is uniform Field inside cavity is along a Field inside cavity is perpendicular to a Back 8 Mark for Review Next If an alartenn ic neniantar with watocit illl movia ndau start hafera entiring with payitvall 8 Clear Response A Q X

D A magnet of magnetic moment 507 Am is placed in a magnetic field B 0 51 31 T The torque acting on the magnet is 1 175 k Nm 2 150 k Nm 3 75 k Nm 4 25 37 k Nm

29 A ray of light falls on a transparent sphere with centre at C as shown in figure The ray emerges from the sphere parallel to line AB The refractive index of the material of sphere is 1 2 6 3 12 20 A 60 C B 2 3

A particle moves in space such that its velocity and at certain point is given by acceleration V v 41 m s and a 61 2 6k m s The magnitude of component of acceleration in the direction of velocity known known as tangential acceleration is

16 3 A child in danger of drowing in a river is being carried downstream by a current that flows uniformly at a speed of m sec The child is 600m from shore and 800m downstream of a helipad when the rescue helicopter sets out and the helicopter follows the same direction throughout the motion If the helicopter 80 proceeds at its maximum speed of m sec 3 with respect to air and air is blowing with velocity of 4m sec perpendicular to river flow velocity as shown then the time in sec taken by helicopter to reach the child Wind 4m s

5 A charged particle q is shot from a large distance with speed v towards a fixed charged particle Q It approaches Q upto a closest distance r and then returns If velocity of q is halved then the closest distance of approach would be 9 1 2 2 3 2 2r 4 4r

lissipated in the 3 k and 20 k resistors and c the power supplied by the current source 3 KQ 21 1kQ 10 mA Figure 2 45 For Practice Prob 2 13 www 5 KQ 22 20 KQ Answer a 15 V 20 V b 75 mW 20 mW c 200 mW

D 13 The stopping potential V in volt as a function of frequency The work function of sodium from the data plotted in the figure will be Given Planck s constant h 6 63 x 10 34 Js electron charge e 1 1 95 eV of line 1 0 6 4 1014 1 0 y o y 2 x 27 04 3 0 12 0 Vo 1 0 2 1 82 eV 2 2 4 v 10 Hz x 4x10 4 No Do 8 6 10 3 1 66 eV Jo 1 6 x 10 19 C JEE Main 2019 4 2 12 eV J

Q7 In a fixed volume container ideal monoatomic gas is kept at room temperature 300 K To what temperature should the container be heated so that the final rms velocity of the gas molecules increases four times the initial velocity O A 1200 K O B 6000 K O C 4800 K O D 3600 K

1 A rectangular loop has a sliding connector PQ of length 1 and resistance R 22 and it is moving with a speed v as shown The set up is placed in a uniform magnetic field going into the plane of the paper The three currents I I and I are P RQ RQ RO 12

A silver ball of radius 4 8cm is suspended by a thread in the vacuum chamber UV light of wavelength 200 nm is incident on the ball for some time during which a total energy of 1 107 J falls on the surface Assuming on an average one out of 103 photons incident is able to eject electron number of photo electron ejected are 1 10 1 2 106 3 108 4 10 2

12 In the experiment of the meter bridge if length corresponding to null deflection is x what would be its value if the radius of meter bridge wire is doubled 1 x 3 4x 2 4 2x

An oceanographer observes that the density of ocean water increases by 0 001 grams per cubic centimeter every 300 meters below sea level If a cubic meter of ocean water at sea level has a mass of 1 027 kilograms what is the density of ocean water in grams per cubic centimeter at 900 meters Note Density is mass divided by volume 1 kilogram 1 000 grams 1 meter 100 centimeters A 1 030 B 103 C 10 3 D 1 03

The efficiency of the cycle shown below in the figure consisting of one isobar one adiabat and one isotherm is 50 The ratio x between the highest and lowest temperatures attained in this cycle obeys the working substance is an ideal gas A x ex 1 B x ex 1 C x ex 1 D x ex 1 P isobar isotherm adiabat V