Basic Physics Questions and Answers

227 tant 20 Light from two coherent sources of the same my of amplitude A and wavelength illuminates the screen The intensity of the central maximum is 1 If the sources were incoherent the intensity at the same point will be a 41 b 21 AVES bjects d

In Young s double slit experiment the fringe width is 1 x 10 m If the distance between the slit and screen is doubled and the distance between the two slit is reduced to half and wavelength is changed from 6 4 x 10 7 m to 4 0 x 10 7 m the value of new fringe width will be 00 15 x 10 m 2 0 10 m 01 25 10 m 25 10 m 4 Marks 4 1

Q At time t 0 terminal A in the circuit shown in the figure is connected to B by a key and an alternating current I t Io cos wt with 10 1A and W 500rads starts flowing in it with the initial 7 6w the key is direction shown in the figure At switched from B to D Now onwards only A and D are connected A total charge Q flows from the battery to charge the capacitor fully If C 20 F R 100 and the battery is ideal with emf of 50 V identify the correct statement s BD A C 20 F www R 1022 A Magnitude of the maximum charge on the capacitor before t clockavice C in the part of the circuit just before t 7 is 1 x 10 C B The current 6w 50V 7T 6w is

A wire of uniform cross section is hanging vertically and due to its own weight its length changes There is a point C on the wire such that change in length AC is equal to the change in length BC Points A B C are shown AC in figure Find BC 1 1 2 2 C Question Type Single Correct Type 3 2 1 B A

An isolated triple star system consists of two identical stars each of mass m and a fixed star of mass M They revolve around the central star in the same circular orbit of radius r The two orbiting stars are always at opposite ends of a diameter of the orbit The time period of revolution of each star around the fixed star is equal to 1 Question Type Single Correct Type 2 3 4 r 2 G 4M m 2 r3 2 GM 2 r 2 G M m m 4 r3 2 m

66 A uniform rod of mass 2 kg and length 1 m lies on a smooth horizontal plane A particle of mass 1 kg moving at a speed of 2 ms 1 perpendicular to the 1 length of the rod strikes it at a distance m from the 4 centre and stops What is the angular velocity of the rod about its centre just after the collision MY 1 a 3 rad s c 1 rad s 1 b 4 rad s 1 d 2 rad s 1 MY

1 The mass and diameter of a planet are twice those of the earth What will be the time period of oscillation of a pendulum on this planet if it is a seconds pendulum on eath 86 1 2s00 4 2 2s 2 2s P165 3 1 2 S

Two plate AB and CD are rigidly attached perpendicular to base of a massive box Box is released on smooth inclined plane having angle of inclination 37 With what minimum speed with respect to box a particle is projected so as to graze top point A and C of plate AB 2m CD 3m Given Separation between top of plate is 3m Take g 10m s Smooth TROP

O implements logic addition O is equivalent to a series switching circuit O is an any or all gate O is equivalent to a parallel switching circuit

ixed inclined plane Find minimum coefficient of friction between baby and the triangular block B sitting on the horizontal surface of triangular block B which is sliding on a frictionless so that baby remains stationary with respect to the triangular block B A Zero B 8 C I D 3

Places A and B are 30 km apart and they are on a straight road Hamid travels from A to B on bike At the same time Joseph starts from B on bike travels towards A They meet each other after 20 minutes If Joseph would have started from B at the same time but in the opposite direction instead of towards A Hamid would have caught him after 3 hours Find the speed of Hamid and Joseph 000 N51ZCL

Two mercury drops one of radius 2 mm and the other of radius 1 mm coalesce to form a single drop Find the change in the free surface energy S T of mercury 0 544 N m

An open pipe is suddenly closed with the result that the second overtone of the closed pipe is found to be higher in frequency by 100 Hz than the first overtone of the original pipe The fundamental frequency of open pipe will be a 100 Hz b 300 Hz c 150 Hz d 200 Hz

the given circuit the AC source has w 100rad s Considering the inductor and capacitor to be ideal the correct choice s is are A The current through the circuit I is 0 3A B The current through the circuit is 0 3 2A C The voltage across 1000 resistor 10 2V D The voltage across 500 resistor 10V 100 F 0 5H mooooowwww I 10092 5092

13 Two balls X and Y are thrown from top of tower one vertically upward and other vertically downward with same speed If time taken by them to reach the ground is 6 sec and 2 sec respectively then the height of the tower and initial speed o each ball are g 10 m s2 A 60 m 15 m s 0 20 B 80 m 20 m s 10

4 50 NUI RICALS a A district is 40 km long and 18 km wide Find the area of district in i hectares ii m b A tennis ball is of diameter 7cm What is its volume in i cm ii m c The level of water in measuring cylinder is at 12 5 ml When a stone is lowered in it carefully The new volume recorded is 21 ml What is the volume of the stone

Which statement is correct for p type semiconductor 1 the number of electrons in conduction band is more than the number of holes in valence band at room temperature 2 the number of holes in valance band is more than the number of electrons in conduction band at room temperature 3 there are no holes and electrons at room temperature 4 number of holes and electrons is equal in valence and conduction band 45 de l pro 3 A moc gair is resp 1 3

When the current in a certain inductor coil is 5 0 A and is increasing at the rate of 10 0 A s the potential difference across the coil is 140V When the current is 5 0 A and decreasing at the rate of 10 0 A s the potential difference is 60 V The self inductance of the coil is Question Type Single Correct Type 1 2H 2 4H 3 8H

Q An AC voltage source of variable angular frequency and fixed amplitude Vo is connected in series with a capacitance C and an electric bulb of resistance R inductance zero When w is increased A the bulb glows dimmer B the bulb glows brighter C total impedance of the circuit is unchanged D total impedance of the circuit increases JEE 2010

capacitors is shown with a switch S and battery B The ratio energy of capacitors system when switch is closed to the situation when switch is open S O O A 2 1 B 4 3 C 3 2 D 3 4 B

b c greater for d equal but not 30 for both the colors 66 A ray of light passes through an equilateral prism refractive index 1 5 such that angle of incidence is equal to angle of emergence and the latter is equal to 3 4th of the angle of prism The angle of deviation is b 30 c 45 d 120 74 75

An electric dipole of moment P is placed in the position of stable equilibrium in uniform electric field of intensity E It is rotated through an angle e from the intial position The potential energy of electric dipole in the position is

c 97 Two plane mirrors are placed parallel to each other at a distance L apart A point object O placed between them at a distance L 3 from one mirror Both mirrors form multiple images The distance between any two images cannot be 3L 2 b 3 c 2L d L 100 A plane the x axi The min object im in front relative a c

6 All of the following apply to the same turbojet a A compressor operates with a pressure ratio of 14 and an efficiency of 0 88 The inlet total temperature is 389 K What is the exit total temperature Assume y 1 40 b The airflow rate of a turbojet is 45 36 kg s Air enters the burner at 611 K total temperature The burner has an efficiency of0 85 and a pressure ratio of 0 93 The fuel has a heating value of 41868 kJ kg and flows at 0 91 kg s Assume cp 1 214 kJ kg K What is the exit total temperature c The turbine pressure ratio is 0 30 and the turbine has an efficiency of 0 83 The incoming total temperature is 1167 K and the mechanical efficiency of the shaft system is 0 98 How much power is delivered to the compressor hp if the airflow rate of a turbojet is 45 36 kg s Assume cp 1 156 kJ kg K and v 1 33

1 0 32 kg m s 3 Zero A block of mass m is kept on a rough horizonta surface having coefficient of friction of 0 5 A horizontal force is applied on the block but th block remains at rest The maximum conta force exerted by the surface on the block can be 1 3 mg 2 R 0 64 kg m s 1 4 1 28 kg m s 1 3 mg 2 3 5 mg 2 4 mg

5 If charge flows through a wire is given by q 3 sin 3t then a Find out the amount of charge flows through the wire at 1 b Find out the current flows through the wire at f second 9 c Find out the area under i t curve from to t I seconds seconds

The current in a wire depends on time as i 5sin 2t Find the charge crossing through a cross section in time interval t 0 to t 17 27 s 1 5 coulomb 2 2 5 coulomb 3 10 coulomb 5 4 coulomb

Two balls of mass 1 kg and 2 kg are thrown upward simultaneously with the same speed If the air exerts a constant and equal force of resistance on the two balls then maximum heights covered by 1 kg and 2 kg are hi and h The correct relation between h and h is 1 h h 3 1 h 2 h h 4 h 2h

The minimum number m of bit strings of positive lengths less than 6 such that there must exist three of these m strings having the same number of zeros and the same number of ones is None of the other choices 19

The value of rms current for circuit shown in figure is 2 2 A Then the CORRECT statement s is are H mmmmmmmm R 100922 C www HH V V 220 V rms V 50 Hz 100 A The value of capacitance is F TU B The power factor of circuit is 1 C The power dissipated in the circuit is 484 watt D The rms current in the circuit increases by 5 times after inductor is short circuited

71 A copper block of mass 2 5 kg is heated in a furnace to a temperature of 500 C and then placed on a large ice block at 0 C What is the maximum amount of ice that can melt Specific heat of copper 0 39 Jg C 1 latent heat of fusion of ice 335 Jg a 1 5 kg c 4 5 kg 00 b 3 kg d 6 kg

6 If x 3sinot and x 4cosot then X A is independent of t X2 C X2 2 1 2 B Average value of x2 x from t 0 to t 0 2 D Average value of x x from t 0 to t 0 is 12 is zero

c 10 cm d 10 cm 7 A real image of an object is formed at a distance of 20 cm from a lens On putting another lens in contact with it the image is shifted 10 cm towards the combination The power of the lens is b 5D a 2 D 6 D c d 10 D 63

A solid sphere is rolling without slipping on rough ground as shown in figure It collides elastically with an identical another sphere at rest There is no friction between two spheres Radius of each sphere is R and mass is m Then linear velocity of first sphere after it again start rolling without slipping is Rough wR 7 7wR WR 10 R

A 25 kg uniform solid sphere with a 20 cm radius is suspended by a vertical wire such that the point of suspension is vertically above the centre of the sphere A torque of 0 10 N m is required to rotate the sphere through an angle of 1 0 rad and then maintain the orientation If the sphere is then released its time period of the oscillation will be 25 kg 20 m ll 4464 U M A Ych glater ar si cel ZU VER M fun fan farz Terima 10 and im zon fix

25 A capacitor is filled with an insulator and a certain potential difference is applied to its plates The energy stored in the capacitor is U Now the capacitor is disconnected from the source and the insulator is pulled out of the capacitor The work performed against the forces of electric field in pulling out the insulator is 4 U Then dielectric constant of the insulator is a 4 b 8 CY5 d 3

a 4 4 m s b 3 1 m s c 5 2 m s d 6 1 m s 45 You are given an arrangement of three point charges q 2q and xq separated by equal finite distances so that electric potential energy of the system is zero Then the value of x is a 2 3 b 1 3 c 2 3 d 3 2

4 A plano convex lens f 20 cm is silvered at plane surface The focal length will be a 20 cm c 30 cm b d 40 cm 10 cm 72 W de c

A man of mass 50 kg is standing on a horizontal platform 1 50 kg 100 kg of mass 100 kg resting on a horizontal frictionless floor If the man walks to the other end of the platform then dis placement of platform with respect to floor is 50 kg 15 m 100 kg 1 10 m towards right 3 10 m towards left 2 5m towards right 4 5 m towards left ut for a and for a fer 1 10 m 50 kg 15 m 100 kg 2 5m af

40 Five conducting plates are placed parallel to each other Separation between them is d and area of each plate is A Plate number 1 2 and 3 are connected with each other and at the same time through a cell of emf E The charge on plate number 1 is 1 E A d LU E b E A 2d c 2E 2 3 4 15 A d zero

Negative Marks 1 If wrong option is selected Consider what happens when you jump up in the air Which of the following is the most accurate statement O You are able to spring up because the earth exerts a force upward on you which is stronger then downward force you exert on the earth Since the ground is stationary it cannot exert the upward force necessary to propel you into the air O When you push down on the earth with a force greater than your weight the earth will push back with the same magnitude force and thus propel you into the air When you jump up the earth exerts a force F on you and you exert a force F on the earth You go up because F F2 and this is so because ratio of F to F2 is earth s mass ratio to your mass

A particle moves in a straight line with m s where u is its acceleration 3u velocity at time 1 Initially the particle is at O a fixed point on the line with velocity u Find in terms of u the time at which the velocity is zero

A cubical box of side of 1 meter contains helium gas atomic weight 4 at a pressure of 100 N m During an observation time of 1 second an atom traveling with the root mean square speed parallel to one of the edges of the cube was found to make 500 hits with a particular wall without any collision with other atoms Take R 25 3 J mol K and k 1 38 x 10 2 J K Evaluate the temperature in K of the gas

A car of mass m is moving on a horizontal circular track If coefficient of static friction between the road and the tyres of the car is 0 75 then the maximum contact force acted by the road on the car is 1 3 mg 4 4mg 5 2 4 5mg 4 7mg 4 oth light pulley

4 If a 3t 2r 1 m s is the expression according to which the acceleration of a particle varies Then a Find the expression for instantaneous velocity at any time t will be if the particle was initially at rest b What is the change in velocity after 3 seconds of its start c Find displacement of the particle after 2 seconds of start

The breaking tension of a string is 10 N A particle of mass 0 1 kg tied to it is rotated along a horizontal circle of radius 0 5 metre The maximum speed with which the particle can be rotated without breaking the string is A 5 m sec B 50 m sec D 1000 m sec C 500 m 3 5 7 9

Which of the following is incorrect for se cucumber 1 Belongs to phylum Echinodermata 2 Triploblastic and coelomate 3 Possess water canal system 4 Undergnes external fertilisation

96 An electric field given by E 41 3 y 2 acts within a Gaussian cube of side 1 m placed at origin such that its three sides represent x y and z axis The magnitude of net charge enclosed within the cube is a 480 c 580 b 30 d zero

When a dielectric slab of thickness 4 cm is introduced between the plates of parallel plate condenser it is found that the distance between the plates has to be increased by 3 cm to restore the capacity to it s original value The dielectric constant of the slab is

A solenoid has an inductance of 50 mH and a resistance of 0 025 0 If it is connected to a battery how long will it take for the current to reach one half of its final equilibrium value Question Type Single Correct Type 1 1 39 s 2 1 2 s 3 6 32 s