Physics Questions

In an LCR circuit capacitance is changed from C to 2C For the resonant frequency to remain unchanged the inductance should be changed from L to 1 4L 3 L 2 2 2L 4 L 4

18 The surface density of a circular disc of radius a depends on the distance as p r A Br The moment of inertia about the line perpendicular to the plane of the disc is A 2a 3 c 2 a 2 5 B A Ba 2 5 A b a 4 2B 2 5 d None of these

A particle of mass m is kept on a smooth cube of mass M and side L as shown in figure Cube start moving with a constant velocity v Displacement of the center of mass along the horizontal direction when particle hit the ground is 2L g 2L g A C mv L m M v Mv L m M v B D 2L m ML V g mv Mv V 2L m ML V q M m smooth

A car has a fresh storage battery of e m f 12 V and internal resistance 2 x 10 2 2 If the starter motor draws a current of 80 A Then the terminal voltage when the starter is on is A 9 3 V B 12 V CY 8 4 V D 10 4 V

7 In the given figure net magnetic field at O will be a c 0 0 O a 0 i 2 oi 4 37 2 0 4 7 2a 0 3a 0 b d Hoi 37 4 7 Moi 4 7 3m

During measurement of kinetic energy T the percentage error in measurement of mass of particle and momentum of particle are 2 and 3 respectively The percentage error in measurement of kinetic energy is a 2 b 5 c 3 d 7

Two charges of magnitude 5 nC and 2 nC one placed at points 2 cm 0 0 and x cm 0 0 in a region of space where there is no other external field If the electrostatic potential energy of the system is 0 5 J The value of x is 1 20 cm 2 80 cm 3 1

29 The current flown through the battery connected with infinite network as shown in the figure is 10 V 1Q www 1 5 A 2 10 A 3 2 A 1Q www 292 122 ww 202 ndation imited 19 www 3202

2 A bar magnet of magnetic moment M is placed at a distance D with its axis along positive X axis Likewise second bar mag net of magnetic moment M is placed at a distance 2D on positive Y axis and perpen dicular to it as shown in the figure The mag nitude of magnetic field at the origin is B HOM 4 D Assume D l where l is the length of magnets The value of a must be b N 2D OD 15 S N S X 17 9

A body is projected vertically with a speed of 20 m s in a region where g 10 m s The distance travelled in 3 seconds is a 15 m 20 m b 25 m d 30

The blocks A B are of masses 3 kg and 5 kg respectively The inclined plane is smooth Assume g 10 m s The contact force between the blocks A B in the cases a and b are take g 10 m s a AB 30

A boy whirls a stone of small mass in a horizontal circle of radius 1 5 m and at height 2 9 m above level ground The string breaks and the stone flies off horizontally and strikes the ground after travelling a horizontal distance of 10 m What is the magnitude of the centripetal acceleration of the stone while in circular motion

8 A triangular prism of mass M with a block of mass m placed on it is released from rest on a smooth inclined plane of inclination 0 The block does not slip on the prism Then e M Smooth Fig 7 296 a The acceleration of the prism is g cos 0 b The acceleration of the prism is g tan 0 c The minimum coefficient of friction between the block and the prism is min cot 0

6 0 A vessel of volume 100 liter contains an ideal gas at pressure P and temperature T Gas is continuously pumped out of the vessel at a constant volume rate 5 lit sec kepping the temperature constant The pressure of a gas being taken out equals the pressure inside the vessel then find out time after which pressure Po of gas becomes 100 1 40 3 92 2 80

the 6 Show that a ray of light reflected from a plane mirror rotates through an angle 20 when mirror is rotated through an angle 0 about its axis perpendicular to both the incident ray and 08 al enem the normal to the surface 5

43 Interference fringes are being produced on screen XY by the slits S and S In figure the correct fringe locus is S W3 S a PQ C W3W4 S 1 2 W P W b W W d XY Q W4

If block A shown is moving with speed V as observed by a person on ground then the magnitude of velocity of A with respect to the block B is the wedge is fixed 3 A V B 2 C V 3 D Zero 30

A rocket starts moving upwards with gases ejecting at a rate of 2000 m s relative to itself After 2 minutes its fuel burns out and its mass reduces to 1 5 of its initial value then its velocity at that instant will be 1 1021 m s mm 2 4048 m s

1 16 The circuit shown in the figure is equivalent to a load of of ww 4 a ohms 3 c 4 ohms 292 492 b 813 1 ohms d 2 ohms 21

68 A metre stick weighing 240 g is pivoted at its upper end in such a way that it can freely rotate in a vertical plane through this end figure 10 E12 A particle of mass 100 g is attached to the upper end of the stick through a light string of length I m Initially the rod is kept vertical and the string horizontal when the system is released from rest The particle collides with the lower end of the stick and sticks there Find the maximum angle through which the stick will rise mahsin 37 2 m zg ml 1m M cose

A pipe of circular cross section of inner radius r and outer radius 2r is bent into a semi circle as shown in the diagram A fluid of density p 10 kg m is flowing through it The breaking stress of the material of the pipe is 3 x 10 N m The maximum velocity with which the fluid can flow in the pipe is kx 100 m s Find value of k 9

Unpolarised light is incident fro plane surface of a material of refractive inde u At a particular angle of incidence i it is found that the reflected and refracted rays are perpendicular to each other Which of the following options is correct for this situation a i sin b Reflected light is polarised with its electric vector perpendicular to the plane of incidence c Reflected light is polarised with its electric vector parallel to the plane of incidence d i tan

13 A triple slit experiment is performed as shown in the figure with monochromatic light of amplitude au SMS N 8 The graph between resultant amplitude A versus 8 is plotted Choose the correct option s A B C D 42 3 A A20 Sol A C A10 A 20 A 0 2 2n S 2 d 21 3 S S S N 2 2 3 52 42 22 3 3 3 3 M 0 N A A 3 AN RIN N 3 2 D d 27 3 22 2 42 3 3 1 A20 42 3 A10 52 3 A10 A20 8 screen 8 2 where A1o and A20 are the values shown in option A A 0 5 where A10 and A20 are the values shown in option A A10 A20

DE021B0AH ANTARGE 3 6 mm 4 4 mm A parallel beam of fast moving electrons is incident normally on a narrow slit A fluorescent screen is placed at a large distance from the slit If the speed of the electrons is increased which of the following statements is correct 1 The angular width of central maximum will be N unaffacted 9 2 Diffraction pattern is not observed on the screen in the case of electrons cleach 3 The angular width of the central maximum of the diffraction pattern will increase 4 The angular width of the central maximum will decrease dif us C

2 k Electric field in a region is found to be E 3yj The total energy stored in electric field inside the cube shown will be A 9a C a B 3 a D 0 D None of these Z a AY 0 a

ladder N Mg 14 The door of an almirah is 6 ft high 15 ft wide and weighs 8 kg The door is supported by two hinges situated at a distance of 1 ft from the ends If the magnitudes of the forces exerted by the hinges on the door are equal find this magnitude 53 A b angu ball pul If mor

5 A light ray travelling in glass medium is incident on glass air interface at an angle of incidence 0 The reflected R and transmitted T intensities both as function of 0 are plotted The correct sketch is IIT JEE 2011 100 a Intensity c 0 100 Intensity T R 0 T R 90 0 0 90 b 100 d Intensity 0 100 Intensity 0 T R T R 0 90 0 90

34 Density of ice is p and that of water is o What will be decrease in volume when a mass M of ice melts 1 M o p 1 3 M 2 4 o p M M 10

3 Magnetic force acting on the charged particle projected perpendicular to magnetic fiel proportional to v where v is the speed Find n Magnetic force acting on 41

A particle is projected upwards with velocity 60 m s In 8 s Average velocity of the particle is A 20 m s B 40 m s Average speed of the particle is B 60 m s A 30 m s 48 49 C 80 m s C 42 m s D 60 m s D 25 m s

DIOCK OI kg is lying on horizontal surface The static friction between the block and the surface of table is 0 5 What is the minimum value of force for motion of the block A 3 43 N C 343 No B 34 3 N D 3430 N

2 1 5 3 19 13 The combination of NOR gates shown here is equivalent to 1 OR B 2 AND 3 NAND 4 19 1 4 XOR of different fr

A particle moving in a straight line covers first half of the distance into two equal time intervals with speed of 2 m s and 4 m s respectively and second half with the speed of 5 m s The average speed of the particle is 1 4 75 m s 2 4 25 m s 3 4 00 m s 27

The definition of average velocity is a the average acceleration multiplied by the time b distance travelled divided by the time 1 c final velocity initial velocity 2 d displacement divided by the time

11 The increase in pressure required to decrease the 200 L volume of a liquid by 0 008 in kPa is Bulk modulus of the liquid 2100 MPa is 1 8 4 2 84 3 92 4 4 168

A rectangular tank of mass m and charge Q over it is placed on a smooth horizontal floor A horizontal electric field E exists in the region Rain drops are falling vertically in the tank at the constant rate of n drops per second Mass of each drop is m Find velocity of tank as function of time

Example 6 12 In the arrangement shown in figure JA 4 0 kg and mg 1 0kg The system is released from rest and block B is found to have a speed 0 3 m s after it has descended through a distance of 1m Find the coefficient of friction between the block and the table Neglect friction elsewhere Take g 10 m s Solution From constraint relations we can see that VA 2VB Therefore 19 2 03 06ml A Fig 6 2

A thin circular ring of mass m radius R has a uniformly distributed charge Q The ring is placed on a rough horizontal floor The coefficient of friction between the ring and the floor is u A uniform vertically upward magnetic field of radius greater than R and co axial with the ring exists in the space The magnetic field is changing as B Bot tesla where t is the time in second where Bo is a positive constant Now answer the following questions based on the above paragraph b umg Find the Time at which the Ring Starts Rotating 4 Mmg 3B QR BQR M

A ship of mass 2 107 kg initially at rest is pulled by a force of 5 105 N throug distance of 2 m Assuming that the resistance due to water is negligible the spee the ship is 1 A 2 ms B 0 01 ms 1 C 0 1 ms D 1 ms E 5

49 A Carnot engine having an efficiency of n 1 10 as heat engine is used as a refrigerator If the work done on the system is 10 J the amount of energy absorbed from the reservoir at lower temperature is JEE MAIN 2007 Coefficient of performance of refrigerator

AL In which of the following cases the contact force between A B is maximum m mg 1kg g 10ms 2 1 50 N 2 3 A B A A 30N B B a 35ms a 25 ms

30 Two steel rods and an aluminium rod of equal length l and equal cross section are joined rigidly at their ends as shown in the figure below All the rods are in a state of zero tension at 0 C Find the length of the system when the temperature is raised to 0 Coefficient of linear expansion of aluminium and steel area and a respectively Young s modulus of aluminium is Y and of steel is Y Steel 1390 Aluminium Steel O

23 A body is initially at rest It undergoes one dimensional motion with constant acceleration The power delivered to it at time t is proportional to 1 1 t2 O 3 n 2 t 4 2

36 u V graph for the virtual image due to a concav mirror can be plotted as 1 3 2 u

1 The focal length of a concave mirror is f and the distance from the object to the principal fo is x Then find the ratio of the size of the image to the size of the object

A uniform rod of length L lies on a smooth horizontal table A particle moving on the table strikes the fod perpendicularly at an end and stops Find the distance travelled by the centre of the rod by the time it turns through a right angle Show that if the mass of the rod is four times that of the particle the collision is elastic 66

A mass of 1g carrying charge q falls through a potential difference V The kinetic energy acquired by it is E When a mass of 2g carrying the charge q falls through a potential difference V What will be the kinetic energy acquired by it a 0 25 E b 0 50 E c 0 75 E d E

The quantum levels of atoms of hydrogen and deuterium are only approximately the sam The difference between the two systems of levels is exaggerated in the figure n n 5 n n 5 n 4 n 4 n 3 n 3 n 2 n 1 System 1 System 2 n 2 n 1 Select the correct statement s A System 1 belongs to hydrogen and 2 to deuterium B System 1 belongs to deuterium and 2 to hydrogen C Greater the mass of the nucleus greater the separation of the energy levels D Greater the mass of the nucleus lesser the separation of the energy levels

A The position of centre of mass relative to body is independent of the choice of coordinate system R Centre of mass does not shift its position in the absence of an external force

34 Two bodies A and B of masses 5 kg and 10 kg in contact with each other rest on a table against a rigid wall Fig 5 21 The coefficient of friction between the bodies and the table is 0 15 A force of 200 N is applied horizontally to A What are a the reaction of the partition b the action reaction forces between A and B What happens when the wall is removed Does the answer to b change when the bodies are in motion Ignore the difference between and u 200 N Fig 5 21