Physics Questions

The figure shows an infinite ladder of resistances The resistance in the n th rung of the ladder counted from left is n n 1 ohms A B The effective resistance between the points A and B is A 0 1 B 2 C 2 3 22 622 12 2002 D10

cm B 15 Two vertical conducting cylinders A and B of different cross sections are connected by a thin tube as shown An ideal gas is trapped in the cylinders by two airtight pistons of masses 1 0 kg and 2 0 kg respectively Initially the pistons are at the same height 40 cm above the base of the cylinders If an additional mass of 10 g were gently placed on the piston in the cylinder A which of the following statements correctly describe the new steady state ultimately reached a Pressure of the gas has been increased b Pressure of the gas remains unchanged c Height difference between the pistons becomes 30 cm d Height difference between the pistons becomes 60 cm 16 Two rubber balloons filled with the same ideal gas wh

magnification produced by an astronomical telescope for normal adjustment is 10 and the length of the telescope is 1 1 m The magnification when the image is formed at the least distance of distinct vision is 1 6 2 16 80 The 2 14 1 18

99 Light is incident on a right angle prism as shown in figure On the hypotenuse of prism a drop of liquid is placed The refractive index of prism is 1 62 The maximum refractive Index that the liquid may have if the light is to be totally reflected is O A 1 52 O 11 1 38 O c 1 40 O 0 1 62 30 bround to have full cireu view of the roomurrou

A load W is to be raised by a rope from rest to rest through a height a the greatest tension which the rope can safely bear is nW Then the least time in which the ascent can be made is 1 Zero 2 3 na n 1 2na n 1 g 1 2 of these

15 Which of the following statement s is are 1 correct I Atoms or molecules in a fluid are arranged in a random manner II A fluid can withstand tangential or shearing stress for an indefinite period III A fluid has no definite shape of its own 1 Only I 2 Both I and III 3 Only III 4 All of these

Q12 Two plane mirrors intersect at right angles as shown in figure A light ray incident on first mirror at a point 12 cm from their point of intersection The angle of incidence at first mirror for which the light ray strikes the midpoint of second mirror is O A 60 O 8 30 O C 45 12 00 around to have full circulos view of the roomsurround

4 None of these 31 Two vessel of the same volume contain the 31 same gas at same temperature If pressure in the vessel are in ratio of 1 2 then 1 Ratio of v is 1 2 rms 2 Ratio of average kinetic energy is 1 1 3 Ratio of average velocity is 1 2 4 Ratio of number of molecules is 1 2 4 473 474 1 v 2 a 3 a 4 1 2 1 2 1 2 1

1 Equal masses of water and a liquid of relative density two are mixed together then mixture has a relative density of 1 2 3 2 4 3 3 3 2 4 3 essel contains a liquid of density p as shown 2 pressure at the point P is no e fufera fe 1 2 3 farger

12 cm s When water spreads on a glass plate the for between the water molecules and glass mo ecules is called 1 Surface tension 2 Cohesive force 3 Adhesive force 4 None of the

0 Identical balloons are connected through identical valves with two identical cylinders One cylinder contains gaseous helium and the other gaseous nitrogen Both the gases may be assumed ideal and both the cylinders weigh equally Which balloon will be inflated faster when the valves are opened and why a The nitrogen balloon will be inflated faster because nitrogen is a heavier element and so the molecules of nitrogen have greater momentum and thus force the balloon to expand at a greater rate b The helium balloon will be inflated faster because helium is a lighter element and so its atoms move faster and can get into the balloon at a greater rate c The helium balloon will be inflated faster because the helium must be at higher pressure and hence the gas will be forced into the balloon at a greater rate d It will depend on whether the gases have to flow up or down to enter the balloon Helium being lighter than air as compared to nitrogen will rise faster than nitrogen Therefore if the balloons are at the top of the cylinders the helium balloon will be inflated faster and if they are at the bottoms the nitrogen balloon will be inflated faster

A particle moves along a straight line w ith its velocity related to position as v xxx2 where a constant If at t 0 x 0 and v 0 then find the following i Acceleration in terms of displaceme nt ii Acceleration in terms of time

4 volumes of A B and C will become equal at equilibrium A volume V of a viscous liquid flows per unit 8 time due to pressure head of AP along a pipe of diameter D and length 7 Instead of this pipe a set of four pipes each of diameter D 2 and length 27 is connected in parallel to the same pressure head of AP Now the volume of the liquid flowing per unit time is 1 V 2 V 4 3 V 6 4 V 8

Q6 There is no SI base unit for area because O A We live in a three not a two dimensional world O B Area can be expressed in terms of square meters O c An area has no thickness hence no physical standard can be built O D It is impossible to express square feet in terms of meters

83 In young s double slit experiment 8th maximum of wavelength is at a distance x from its central maximum and 4th maximum of wavelength 22 is at a distance x from its central maximum The ratio X will be

A body is moving through a viscous fluid then choose the incorrect option 1 Viscous force acting on the body depends on density of body 2 Viscous force acting on the body depends on viscosity of fluid 3 Viscous force acting on the body depends on velocity of body 4 Viscous force acting on the body is directed opposite to the direction of l

4 Height of The given figure shows three soap bubbles A 7 B and C are prepared by blowing the capillary tube with stop cocks S S S and S With stop cock S closed and S S and S opened then A S HS HIS L E B 1 C and A will both start collapsing with volume of B increasing 2 B will start collapsing with volumes of A and C increasing 3 C will start collapsing with volumes of A and B increasing 4 volumes of A B and C will become equal at equilibrium liquid flows per ur

When an air bubble comes from the bottom of a lake to the top surface then its radius 1 Increases 2 Decreases 3 Does not change 4 Becomes zero

Q1 Light is incident on a right angle prism as shown in figure On the hypotenuse of prism a drop of liquid is placed The refractive index of prism is 1 62 The maximum refractive index that the liquid may have if the light is to be totally reflected is 60 90 Liquid drop 30

1 When a thin transparent plate of refractive index 1 5 is introduced in one of the interfering beams a shift of 20 fringes is observed If it is replaced by another thin plate of half the thickness and of refractive index 1 7 the number of fringes that will be 1 23 3 28 4 7 undergo shift EN PAR

In the circuit shown the switch S is shifted to position 2 from positi on 1 at t 0 having been in positi on 1 for a long time The current in the circuit as a function of time is I a b e ct where a b and c are constants in SI units Find the value of ac b 1 S 00000 10 H www 5 H 00000 40 V

Q5 A perfect gas in a closed container is maintained at an initial pressure P If all the atoms are replaced by another species of mass half that of the first and their speeds are made double what will be the resultant pressure O A 2 P O B P12 O c Pi D 4 Pipidl

The figure below shows Atwood s machine in which two containers are connected by a cord of negligible mass passing over a frictionless pulley also of negligible mass At time t 0 container 1 has mass 1 30 kg and container 2 has mass 3 16 kg but container 1 is losing mass through a leak at the constant rate of 0 274 kg s IN a At what rate is the acceleration magnitude of the containers changing at t 0 3 4849 x m s b At what rate is the acceleration magnitude of the containers changing at t 3 00 s 7 7948 x m s c When does the acceleration reach its maximum value Draw a free body diagram for container 1 and another one for container 2 Write Newton s second law for container 1 and also for container 2 The upward force on each is the same pull from the rope Assume container 2 accelerates down the y avis container 1 has the same magnitude of acceleration Once acceleration is determined in terms of m differentiate the expression with respect to time

3 A ball of mass 10 gram and charge 107C moves from point A whose potential is 500 V to another point B whose potential is zero The velocity of the ball at the point B if its velocity at the point A is zero is 1 0 1 ms 3 10 ms G 2 0 01 ms 4 100 ms

27 180 The diagram shows the energy levels for an electron in a certain atom Which transition shown represents the emission of photon with the maximum energy n 4 n 3 I I Mark for Review III IV n 2 n 1

A particle oscillating under a force F KX bv is K and b are constants then oscillator is 1 Simple harmonic oscillator 2 Linear oscillator 3 Damped oscillator 4 Forced oscillator

5 ncrease An ideal gas changes in states from 1 to 2 through three different processes A B C as shown 10 A B C 4 25 A V Then work done during the processes are WA WB W Choose the correct option 1 W W W 3 W WC WB 2 WA WB W 4 WC WA WB A BCsfatda sa P A B 1 HW 1 W W W 3 W W W

Pre Medical Physics 22 A child climbs up a step waited f on step and comes down and process Choose x t graph for th X 0 M 1 2 3 4 X t m In hmm X 0

ALLEN 6 Three tubes A B and C are connected to a 6 horizontal pipe in which an ideal liquid is flowing The radii of the tubes A B and C at the junction are respectively 2 cm 1cm and 2 cm It can be said A B C 1 The height of the liquid in the tube A is maximum 2 Height of the liquid in the tubes A and B is same 2 3 Height of the liquid in the tubes A B and C is same night of the liquid in the A and C is same bubbles A

A solid is completely immersed in an ideal 5 liquid The force exerted by the liquid on the solid will 1 increase if it is pushed deeper inside the liquid 2 change if its orientation is changed keeping it inside the liquid 3 decrease if it is taken partially out of the liquid

executing S H M is shown in fig given below Choose the correct statements vs time curve for a particle 15 displacement Ay 1 Phase of the oscillation is same at t Os and t 2s time s 2 Phase of the oscillation is same at t 2s and t 6s 711 3 Phase of the oscillation is same at t Is and t 7s 4 Phase of the oscillation is same at t Is and t 3 s 1 a d feeigen displacement 2 b c 3 pa 1 t 0s 2 t 2st 2 t 0 72t 2s 3 t 1s 72 t 79 4 t 1s 72 t 3

79 In a glass prism one face is silvered A ray of light falls on the other face at an angle of 45 After refracting at the face it is subsequently reflected from the silvered face and retraces its path If the refracting angle of the prism is 30 the refractive index of the material of the prism is 3 D 2 1 3 3 2 2 2 4 3

5 Two conducting rods A and B of same length and cross sectional area are connected i In series ii In parallel as shown In both combination a temperature difference of 100 C is maintained If thermal conductivity of A is 3K and that of B is K then the ratio of heat current flowing in parallel combination to that flowing in series combination is A B 100 C 3K 16 i 0 C 3 100 C 1 3K K ii 0 C 1

Balloons with constant ascending velocity can be used to investigate wind velocities at various heights The given graph of elevation angle against time was obtained by observing a such balloon The balloon was released at distance L 1 km from the point of observation and it seemed to be rising dir ectly upwards Knowing that wind velocity near the ground was zero find the balloon s height at time t 7 min after its start and wind velocity at this height a deg 60 40 20 0 2 4 6 8 t min

A projectile thrown from ground at some angle is having velocities u and V at two points during it If u and are perpendicular to each other then the minimum kinetic energy during the journey is of the projectile is m A 2 u v u v B m uv 2 u v C m u v 2 u v m u v uv D b

4 Four pendulum A B C and D are suspended from the same elastic support as shown in figure A and C are of same length while B is smaller than A and D is larger than A If A is given a transverse displacement C B A D 1 D will vibrate with maximum amplitude 2 C will vibrate with maximum amplitude 3 B will vibrate with maximum amplitude 4 All the four will oscillate with equal amplitude accillating under a force 5 f FAR a 1 2 3 4 U

A vessel contains a liquid of density p as shown in figure The gauge pressure at the point P is H 1 hpg 3 H h pg H h OF 2 Hpg 4 H h pg cos 0 ubbla comes from the bottom of figur 3 H www 1 hpg 3 H h pg

7 Initially a photon of wavelength falls on a photocathode and emits an electron of maximum energy E If the wavelength of the incident photon is changed to 22 the maximum energy of the emitted electron becomes E2 The value of hC is h planck s constant and C speed of light 2 2 E E E E 2 1 2 2 2 2 3 E E 2 4 21 22 E2 E

Z dl R I O dl X dB 7dB P dBx X FIGURE 4 11 Magnetic field on the axis of a current carrying circular loop of radius R Shown are the magnetic field dB due to a line element dl and its components along and perpendicular to the axis

A ray of light is incident at an angle a at the boundary separating two transparent media The light is transmitted However if the angle of incidence is increased very slightly the ray gets refracted into the incident medium The difference between the angles by which the incident light is deviated in the first case and that in the second case is A 2 B 90 C 180

In case of water from 0 C to 4 C i Volume decreases and density of water is maximum at 4 C ii AW will be negative since volume decreases iii Cp C V iv C C 1 i ii 3 iii iv 2 ii iii 4 i ii iv 17 18 ALLEN 0 C 4 C affery 1 4 C 1 iii C C iv C C 1 i ii 3 iii iv 2 ii iii 4 i ii iv

4 None of the above A piston is slowly pushed into a metal cylinder isothermally containing an ideal gas them incorrect statement is 1 Pressure of the gas increases 2 Average speed of the gas molecules increases 3 The number of molecules per unit volume increases 4 None of these

in example 15 2 can you explain last 4 steps of solution given in ncert h ow sin 80x0 3 3x20 converted tosin 36 12 WAVES VV Fig 15 7 An element of a string at a fixed location oscillates in time with amplitude a and period T as the wave passes over it y 0 t a sin a sin t Now the period of oscillation of the wave is the time it takes for an element to complete one full oscillation That is a sin t asin t T a sin t T Since sine function repeats after every 2 We then relate the wavelength to k through Eq 15 6 2n k 2x 80 0 m 7 85 cm c Now we relate Tto by the relation T 2r a 2n 3 0 s 2 09 s and frequency v 1 T 0 48 Hz The displacement y at x 30 0 cm and time t 20 s is given by y 0 005 m sin 80 0 0 3 3 0 20 0 005 m sin 36 12m 0 005 m sin 1 699 0 005 m sin 97 5 mm 15 4 THE SPEED OF A TRAVELLING WAVE Here again radian could be dropped and the units could be written merely as mr Thus k represents 2 times the number of waves for the total phase difference that can be accommodated per unit length with Sl units m Example 15 2 A wave travelling along a string is described by ux 0 005 sin 80 0 x 3 0 U in which the numerical constants are in Si units 10 005 m 80 0 rad m and 3 0 rad s Calculate tal the amplitude b the wavelength and c the period and frequency of the wave Also calculate the displacement of the wave at a distance x 30 0 cm and time t 20 s Answer On comparing this displacement equation with Eq 15 2 y x t a sin kx ot we find a b the amplitude of the wave is 0 005 m 5 mm the angular wave number k and angular frequency o are k 80 0 m and 3 0 s 2mv 2rk V a distance Ax in time At The speed of the wave is then Ax At We can put the cross on a point with any other phase It will move with the same speed otherwise the wave pattern will not remain fixed The motion of a fixed phase point on the wave is given by kx at constant 15 10 Thus as time t changes the position x of the fixed phase point must change so that the phase remains constant Thus kx wot klx Ax 1 Al or k Ax At 0 Taking Ax At vanishingly small this gives dx dt k Relating to Tand k to A 369 D A Av T En 15 12 a general relation for all 15 12

A uniform rod of mass 10 kg and length 2 m is placed along x axis such that its one end is at the origin Moment of inertia of the rod about z axis is 1 3 40 kg m 12 20 kg m 12 2 4 20 3 kg m 40 kg m 3

a given process on an ideal gas dW 0 24 dQ 0 then for the gas 1 Temp will decrease 2 Vol will increase 3 pressure will remain constant 4 Temp will increase a felu 1 2 34 3 fram 4

Q4 a The intrinsic carrier density at room temperature in Ge is 2 37 x 10 9 m if the electron and hole mobilities are 0 38 and 0 18 m V s respectively calculate the resistivity b The intrinsic carrier density is 1 5 10 6 m If the mobility of electron and hole are 0 13 and 0 05 m V s calculate the conductivity

A body is dropped from the top of a tower of height 3h The ratio of the intervals of time to cover the three equal heights h is Ot 12 t3 1 3 5 Ot t t3 1 2 5 t t O t t t3 3 2 1 O t t t3 1 2 1 3 2

The figure shows a system consisting of 1 a ring of outer radius 3R rolling clockwise without slipping on a horizontal surface with angular speed oo and ii an inner disc of radius 2R rotating anti clockwise with angular speed wo 2 The ring and disc are separated by frictionless ball bearings The system is in the x z plane The point P on the inner disc is at a distance R from the origin where OP makes an angle of 30 with the horizontal Then with respect to the horizontal surface 2012 3R Z w 2 R 30 2R X a the point O has a linear velocity 3Rwi b the point P has a linear velocity Roi 11 4 13 4 c the point P has a linear velocity d the point P has a linear velocity Rw 3 Rol 4 3 4 Ro

As shown in figure two identical capacitors are connected to a battery of V volts in parallel When capacitors are fully charged their stored energy is U If the key K is opened and a material of dielectric constant E 2 is inserted in each capacitors their stored energy is now U Then r 5 5 U 1 will be V 3 5 HH C 2 K 5 3 C

6 Heat is flowing steadily from A to B 6 Temperature T at point P at distance x from A is such that A X 4 B 1 T decreases linearly with x 2 T increases linearly with x 3 T decreases exponentially with x 4 T increases with x as T a x AB A x A X 1 2 42 2 3 4 xa B