Physics Questions

Monochromatic light of wavelength 667 nm is produced by a helium neon laser The power emitted is 9 mW The number of photons arriving per sec On the average at a target irradiated by this beam AIPMT Prelims 2009 is 2 9 1015 4 9 1017 1 3 1016 3 3 1019

simple harmonic motion is given by y A Asinot Bcoswt Then the amplitude of its oscillation is given by 2 1 Ao A B lo 2 A B ions 3 A2 A 4 A B s Limited

23 A stationary hydrogen atom of mass M emits a photon corresponding to the second line of Lyman series If R is the Rydberg constant the velocity tha the atom acquires is 1 Rh 2M 8Rh 2 Rh M Rh

Two objects are connected to a rope and the rope is hung over a pulley connected to the ceiling as shown in the figure below M1 MOR My The masses of the objects are m 16 0 kg and m 11 0 kg the mass of the pulley is M 5 00 kg and the radius of the pulley is R 0 300 m Object m is initially on the floor and object m is initially 4 80 m above the floor when it is released from rest The pulley s axis has negligible friction The mass of the rope is small enough to be ignored and the rope does not slip on the pulley nor does it stretch a How much time in s does it take object m to hit the floor after being released At b How would your answer to part a change if the mass of the pulley were neglected Enter the time in seconds it takes object m to hit the floor if the mass of the pulley were neglected

A person climbs up a stalled escalator in 60 s standing on the same but escalator running with constant velocity he takes 40 s How much time is taken by the person to walk up the moving escalator a 37s b 27s c 24 s d 45 s

100 2002 2002 4092 and 5092 are connected as shown in figure The equivalent resistance between points A and B is C 10 2 A www 20 2 209 50 2 B 40 9 53 D 10 109 a 40 b 60 2 c 2002 d 30 2

has half the mass When E becomes peed of the m s m s from origin ith position mx 3 37 If F 2x 3x 2 then select the correct statement 1 1 x is the position of stable equilibrium 2 2 x 2 is the position of stable equilibrium 1 is the position of unstable equilibrium 2 3 X 4 x 2 is the position of neutral equilibrium 38 When a conservative force does positive work on a body then the

hydrogen atom If the ionisation potential in the ground state for hydrogen is 13 6 e V then find the excitation potential of third orbit hit to ground state of hydrogen atom then calculate the wavelength of

velocity vector and perpendicular to each other is equal to 1 1 sec 2 2 sec 3 1 5 sec 4 5 sec At any instant of time acceleration and velocity of a particle are given by j v 6 8 then rate of change of speed at the same instant will be 3 4 25 3 3 8 1 2 61 81 25 4 31 4

D A block of mass m is pushed against a spring of spring constant k fixed at one end to a wall The block can slide on a frictionless table as shown in figure 8 W6 The natural length of the spring is Lo and it is compressed to half its natural length when the block is released Find the velocity of the block as a function of its distance x from the wall k 0000000 Lo 2 m

In a Young s double slit experiment the slits are placed 0 320 mm apart Light o wavelength 500 nm is incident on the slits The total number of bright fringes that ar observed in the angular range 30 0 30 is A 640 C 321 B 320 D 641 7 19 pm

3 180 3A 4 180 3A 34 Rays from a lens are converging toward a point P as shown in figure How much thick glass plate having refractive index 1 8 must be located between the lens and point P so that the image will be formed at P 1 5 cm 3 0 9 cm Glass plate 2 2 4 cm 4 1 6 cm PP 0 4 cm

15 16 For Questions 15 16 A block of mass 2 kg is placed on a rough horizontal surface A spring is attached to the block whose other end is joined to rigid wall as shown in the figure A horizontal force is applied on the block so that it remains at rest while the spring is elongate mg k by x x2 Let Fmax and Fmin be the maximum and minimum values of force F for which the block remains in equilibrium For a particular x Fmax Fmin 4N Also shown is the variation Fmax Fmin versus x the elongation of the spring g 10 m s2 mmmmmmmm 2kg The spring constant of the spring is A 20 N m B 25 N m The value of Fmin if x 6 cm is A 1 50N B 0 d F Fm Fin 10N C 30 N m C 2N 0 2m X D 40 N m D 1N

Two point masses of mass m and 2m placed on smooth horizontal plane are connected by a light rod of length Masses are given velocities in horizontal plane perpendicular to rod as shown If area of cross section of rod is A and Young s modulus is Y then elongation in the rod will be A B C D mv AY 2mv AY 6mv AY 3mv AY m Vo 200 2m

54 A body of mass M and volume V is floating in a liquid of density o When an excess mass m is placed on the body then it just sinks in the liquid The value of excess mass is 1 Vo M 3 M Vo 2 Vo M Vo M 4 Vo

An aluminum container of mass 100 gm contains 200 gm of ice at 20 C Heat is added to the system at the rate of 100 cal s The temperature of the system after 4 minutes will be specific heat of ice 0 5 and L 80 cal gm specific heat of A 0 2 cal gm C in C x x 8 1 Find x

15 The activity of a radioactive substance is R at time t and R at time t t Its decay constant is A Then 1 R R 1 1 3 R t constant 2 R R e 2 4 R R e 4 1

33 The refracting angle of a prism is A and refractive index of the material of prism is cot A 2 The angle of minimum deviation will be 2 180 2A 4 180 3A 1 90 3A 3 180 3A

Find the magnitude of the magnetic field induction at the origin O due to a very long conductor carrying current i of the shape shown in figure 1 2 3 4 Ho 2r Mol 2r Hol 4 r Ho 1 12 X

R Problem 1 8 A thin insulated wire form a spiral of N 100 turns carrying a current of i 8mA The inner and outer radii are equal to a 5cm and b 10cm Find the magnetic field at the centre of the coil Solution Let n no of turns per unit length along the radial of spiral Consider a ring of radii x and x dx N ndy n

A rubber ball is released from a height of 5 m mathongo mathongo above the floor It bounces back repeatedly mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo 81 always rising to of the height through 100 mathongo maunongo mathongo mathongo mathongo mathongo which it falls Find the average speed of the ball mathongo mathongo mathongo mathongo mathongo mathongo Take g 10 ms 2 Wmathongo w mathongo mathongo mathongo mathongo mathongo 1 3 0 ms 1 mathongo mathongo mathongo mathongo mathongo mathongo mathongo 4 2 50 ms 1 mathongo mathongo mathongo mathongo mathongo mathongo 2 3 50 ms 3 2 0 ms 14 mathongo mathongo mathongo

The depth of an ocean is about 3000 m Calculate the percentage compression of the water at the bottom of the ocean Bwater 1 5 10 N m 2 1 3 3 6 2 4 0 2

What is the function of the instruction decoder in 8085 O Identifies instruction Determine number of fetch cycle required to fetch current instruction Sends decoded information to timing and control logic unit All of the above

14 A radioactive sample decays with decay constant A A capacitor of capacitance C is charged to some potential and then the plates are connected through a resistance R The value of R such that the ratio of the charge on the capacitor to the activity of the radioactive sample remains constant in time 1 3 2 1 2 ALIC

Threshold wavelength for sodium is 6 x 10 7 m Then photoemission occurs for light of waveleng if 1 6 x 10 7 metre 2 6 x 10 7 metre 3 5 x 1014 metre A Frequency 5 x 1014 Hz

Example 4 4 The position of a particle is given by r 3 0t i 2 0t j 5 0k where t is in seconds and the coefficients have the proper units for r to be in metres a Find v t and a t of the particle b Find the magnitude and direction of v t at t 1 0 s

The rectangular loop shown in the figure is co planar with the straight infinitely long wire carrying current lo The magnetic flux through the loop is 03 Holoa 2T Holob 2T O Holoa 2T Holob In 2 a b

Network shown in the figure is part of a circuit The current is 2 A and is decreasing at the rate of 2 A s Find the value of Vp Vo in volts P 10 V wwwwww 292 2 A 000000 2 H Answer 00 01 02 03 04 05 06 07 08 09 00 01 02 03 04 05 06 07 09

Which factors typically motivate changes to employment laws how often employers get in trouble with the law and the government in power what the government thinks is best for employees and changing social values demographic shifts in society and changing social values

2 The electron in the hydrogen atom jumps from excited state n 4 to its ground state n 1 and photon thus emitted irradiate a photosensitive metal If work function of metal is 2 75 eV the stopping potential is estimated to be 1 4 V 3 10 V 2 2 V 4 5 V

A projectile is thrown in the upward direction making an angle of 60 with the horizontal direction with a velocity of 147 m s Then the time after which its inclination with the horizontal is 45 is g 10 ms 2 1 5 38 s 2 3 15 s 4 2 745 s 10 98 s

riginal orbit The sea level and at top of mountains are w W2 and w3 respectively then b W W W3 dat wy W W3 d w W W3 c w W W3 hody is projected from earth s surface to become qolution will not

7 A certain radioactive material can undergo two different types of decay each with a different decay constant and 22 Then the effective decay constant is 1 2 3 6 2 37 4 4

3 240 nm 4 820 nm 29 A plane wavefront AB is incident on a concave mirror as shown in figure Then the wavefront just after reflection is 1 B 3 2 30 In a Young s double slit experiment 50 fringes are 4 None of these

The particle is moving in a spherical symmetric potential r ar Here w constant Express the average potential energy of the particle in terms of the aven kinetic energy Answer a U T d U 3 r 86 B C D

16 A radioactive nucleus Po210 decays to a stable nucleus Pb206 Then time graph of rate of formation R of Pb206 against time t is best shown by R R 1 h 1 2 4 L I 3 R R Telegram ne

If the frequency of light incident on a metallic plate be doubled how will the maximum kinetic energy of the photoelectrons change 1 It becomes more than double 2 It becomes less than double 3 It becomes exactly double 4 It does not change work funct saturation I and I then as 1 4 2 4 3 4 4 4 Tower 8 Pu

Two spherical vessel of equal volume are connected by a n arrow tube The apparatus contains an ideal gas at one atmosphere and 300 K Now if one vessel is immersed in a bath of constant temperature 600K and the other in a bath of constant temperature 300 K Then the common pressure will be conservo et mall

7 A painter ladder is formed by joining two uniform ladders each 3m long and weighing 150 N Both the ladders are hinged at the apex and are held together by a horizontal tie rope on a smooth floor If a 50 kg load is suspended from the apex as shown in figure then determine the tension in the tie rope 3m 1 6 www Tie Rope 0 5m k4m

A monochromatic point source of light is placed at a distance d from a metal surface Photo electrons are ejected at a rate n per second and with maximum kinetic energy E If the source is brought nearer to distance d 2 the rate and the maximum kinetic energy per photoelectron become nearly 1 2n and 2E 2 4n and 4E 3 4n and E 4 C

A light rod of length L is hinged to a plank of mass m The plank is lying on the edge of a horizontal table such that the rod can swing freely in the vertical plane without any hindrance from the table A particle of mass m is attached to the end of the rod and system is released from 0 0 position a Assume that friction between the plank and the table is large enough to prevent it from slipping The minimum normal force applied by the plank on the table is xx mg Value of x is

2 a nuclear fusion process the masses of fusing nuclei be m and and the mass of product nuclei be m then m stion ape 1 m m m 2 m m m 3 m m m 4 m 11

Figure shows electric field lines in which an electric dipole p is placed as shown Which of the following statements is correct 9 a The dipole will not experience any force b The dipole will experience a force towards right c The dipole will experience a force towards left d The dipole will experience a force upwards

a 0 b 45 3 Two simple pendulums of length 0 5 m and 20 m respectively are given small linear displacement in one direction at the same time They will again be in the phase when the pendulum of shorter length has completed x oscillations where k is a 1 b 3 d 5 c 2 500 m of helium at 27 C 3

13 180 An AC circuit having supply voltage V consists of resistor of resistance 4 Q and capacitor of reactance 3 Q as shown in the figure The voltage across the capacitor at time t B Xc R www V 20 sin of 9 6 V 12 4 V Zero sis

Consider the circuit shown in fig With switch S closed and the other two switches open the circuit has a time constant 0 05 sec With switch S closed and the other two switches open the circuit has a time constant 2 sec With switch S3 closed and the othe two switches open the circuit oscillates with a period T Find T in sec Taken 10 SKA I mmmmm L S C S3 www R THE

A point charge q is placed at a distance 2r from the centre O of a conducting neutral sphere of radius r Due to the induced charge on the sphere the electric potential at point P on the surface of sphere kq is x volt Then find the value of x If 18 volt I 2r TH DI O r P 1

The cathode of a photocell Is work function changes from w to w w If the saturation currents before and after the change are I and 2 and all other conditions are unchanged then assuming hv W 1 2 2 1 3 1 12

In the circuit shown when the input voltage of the base resistance is 10 V VBE is zero and VCE is also zero The value of is 10 V R 10 Vwww 400 k R 3 kQ

2 Two similar coils are kept mutually perpendicular such that their centres coincide At the centre find the ratio of the magnetic field due to one coil and the resultant magnetic field through both coils if the same current is flown 1 2 1 2 3 1 3 1 2