Basic Physics Questions and Answers

21 Physical processes are sometimes described visually by lines Only the following can cross a Streamlines in fluid flow b Lines of forces in electrostatics c Rays in geometrical optics d Lines of force in magnetism

For research purposes a sonic buoy is tethered to the ocean floor and emits an infrasonic pulse of sound The period of this sound is 89 6 ms Determine the wavelength of the sound if temperature the seawater is 20 C

20 A body of mass 800 g freely falls from height of 50 m When this body comes on the surface the earth potential energy completely converts in to kinetic energy Find the loss of potentia energy of a body A 0 J B 200 J C 300 J D 400 J

Two moles of ideal gas initially in the state 1 are put in contact with a thermal reservoir at a temperature of T 400 K and reach through a isochoric irreversible transformation one thermodynamic state 2 T 800 K The specific heat of the gas at constant pressure depends on the temperature and cam be written as c R 2 0 02T Determine the heat Q 2 exchanged in this trasformation O a Q 2 8 65 10 J O b Q 2 200 J O C Q 2 8 65 10 J d Q 2 8 65 10 J

32 Find the acceleration of the block of mass M in the situation shown in figure 5 E15 All the surfaces are frictionless and the pulleys and the string are light M 30 27 2 M Figure 5 E15

6 A jeep runs around a curve of radius 0 3 km at a const speed of 60 ms The jeep covers a curve of 60 arc then incorrect statement is 1 resultant change in velocity of jeep is 60 ms 2 instantaneous acceleration of jeep is 12 ms 3 average acceleration of jeep is approximately 11 5 m s 4 instantaneous and average acceleration are same in case

1 The diagram shows a piece of pure semiconductor S in series with a variable resistor R and a source of constant voltage V Would you increase or decrease the value of R to keep the reading of ammeter A constant wher semiconductor S is heated Give reason A W R S

14 A square plate of mass M and edge L is shown in fig The moment of inertia of the plate about the axis in the plane of plate and passing through one of its vertex making an angle 15 from horizontal is a c ML 12 7 ML 12 115 L b 11ML 24 d none of these

Erica deposited 405 each month into her retirement starting her senior year at FIT She diversified her portfolio so the interest rate averaged to a fixed rate of 9 2 If she was 21 when she started and continued through to age 65 determine the total interest that accumulated to her account A 51 889 54 B 161 950 46 C 2 713 000 42 D 213 840

Electric potential energy possessed by a charge q placed at the equatorial position of an electric dipole P 2qa at a distance r from the centre of the dipole i O Zero O kq a kq a 2 kq 2 2

12 A block A of mass m rests on a horizontal table A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block B of mass m is suspended Th e coefficient of kinetic friction between the block and table is u When the block A is sliding on the table the tension in the string is 2015 a m m g m m c m m 1 g m m b m m 1 g m m d m m g m m

38 When a group of students were formed into groups of 5 or 6 one student was left out on both occasions When they were grouped as groups of 7 nobody was left out What is the least number of students in the group A B C D 91 85 84 63

2 Power delivered by the ac source to the circuit 12 fa becomes maximum when H 1 L C 1 7 2 3 L C If velocity of a particle is given by v 2t 3 m s 13 then average velocity in interval 0 t ls is m s 2 2 L C 4 L C 9 m s 3 4 m s 4 5 m s

The angle between two mirrors is 60 and is kept fixed A ray is incident on one mirror at an angle i as shown in figure The angle i is slowly increased from 0 to 90 The net deviation suffered by the ray after two reflections is D Which of the following plots for magnitude of D vs i is correct 0

An electron is allowed to move freely in a closed cubic box of length of side 10 cm The maximum uncertainty in its velocity will be 1 3 35 x 10 m sec 1 2 5 8 x 10 m sec 3 4 x 105 m sec 6 1

4 None 1 A screen is placed 50 cm from a single slit which is illuminated with 6000 light If distance between the first and third minima in the diffraction pattern is 3 00 mm what is the width of the slit 1 0 1 mm 3 0 3 mm 2 0 2 mm 4 0 4 mm

A circular conducting coil of radius ro having resistance F is placed in a time varying transverse uniform magnetic 4t as shown in the figure The current in the coi at time t 2 s is consider all quantities are in SI units B field B x X x X X X X X X X X X X X X x x x x x x x X X X X X X X X xxx xxx XX XXXXXXX xxx X x x x xok xxxxxxx XXXXXXX X X X X X X X X X X X X X X X X X X X X X 16r R 4 Tr R 8T22 R xxxx

0 33 Lead is good absorber of X rays Specific gravity of Pb 11 5 To cutdown the initial radiation I to 1 2 I a shield of 1 5 cm was used The mass absorption coefficient is La 0 06 cm gm c 0 21 cm 0 462 cm d 0 040 cm gm usted stone The Compton shift in each case

A small block of mass 20 kg rests on a bigger block of mass 30 kg which lies on a smooth horizontal plane Initially the whole system is at rest The coefficient of friction between the block is 0 5 The horizontal force F 50 N is applied on the lower block Find the work done by frictional force on upper block and on the lower block in t 2 s 8 0 5 20 kg 30 kg F 50 N

5 Fresnel s biprism having an angle 1 and index of refraction 1 5 forms interference fringes on a screen placed 80 cms from biprism If the distance between the slit and the biprism is 30 cms find the fringe separation when wavelength of light used is 5000 A Calculate the fringe separation when the distance of 80 cms and 30 cms are interchanges Ans 0 00394 cm

A stationary bomb explodes into two parts masses 3 kg and 1 kg The total KE of the two part after explosion is 2400 J The KE of the smalle part is 1 600 J 2 1800 J 3 1200 J

b dark c 0 47 mm d 0 44 mm White light falls normally on a film of soapy water whose thickness is 5x105 cm and 1 33 W wavelength in the visible region will be reflected most strongly Ans 5230 A

Fresnel s biprism having an angle 1 and index of refraction 1 5 forms interference fringes on a screen placed 80 cms from biprism If the distance between the slit and the biprism is 30 cms find the fringe separation when wavelength of light used is 5000 A Calculate the fringe separation when the distance of 80 cms and 30 cms are interchanges Ans 0 00394 cm

3 Water from a tap emerges vertically downwards with an initial speed of 1 0 ms The cross sectional area of the tap is 10 m Assume that the pressure is constant throughout the stream of water and that the flow is streamlined The cross sectional area of the stream 0 15 m below the tap would be Take g 10 ms 1 1x 10 m LJEE Main 2019 April 4 5 x 10 m 2 5 x 10 m 3 2 x 10 m

The two span continuous beam shown below is supported on three springs having the same constant k 1000 kN m Show all DOFs on a continuous beam sketch and state the beam boundary conditions Construct the structure stiffness relationship F K d for the beam Also determine all beam nodal displacements Consider E 210 GPa and I 4 x 104 m NOTE You Must make use of the beam symmetry 10 kN m 10 kN m Tall 6 0 m 6 0 m

A long heavy flexible rope with mass p per unit length is stretched by a constant force F A sudden movement caused a cirucular loop to form at one end of the loop In a manner similar to that in which transverse waves propagate the loop runs rolls along the rope with speed C as shown in the figure F W F If R is the radius of the loop the energy carried by the loop is A 47 FR B 3 FR C 2 FR D FR In the frame of reference which moves along with the loop with speed C the

c 2 kg d 8 kg 45 A mass Mis suspended from a light spring An additional mass madded displaces the spring further by a distance x Now the combined mass will oscillate on the spring with period a T 2 b T 2 M m X mg M m mg c T 2 d T 2 X M m mg 46 The kinetic energy and potential energy of a particle executing simple harmoni motion will be equal when displacement mg X M m QM

A police siren emits a sound wave of frequency 440 Hz The speed of sound is 330 m s If police jeep moving with speed 20 m s is following a heavy truck moving with 10 m s then frequency of echo from truck heard by a policeman inside the jeep is nearly 1 440 Hz 3 450 Hz 4 480 Hz

m In an oscillating LC circuit the maximum current is I The current through the inductor when the energy is equally shared between the electric and the magnetic fields is A B C D 2018 I 2 I I 2 2 I 2 4

a 5 65 x 10 T c 6 54 x 10 T b 5 27 x 10 T d 9 20 10 T a 1 5 x 10 T c zero 43 A straight wire carrying a current of 13 A is bent into a semi circular arc of radius 2 cm as shown in figure The magnetic field is 1 5x 10 T at the centre of arc then the magnetic field due to straight segment is 87 b 2 5 x 10 T d 3 x 10 T

1 The pair of quantities having same dimensions is 1 Young s modulus and Energy 2 Impulse and Surface Tension 3 Angular momentum and Work 4 Work and Torque

Two waves having the same wavelength but different amplitudes superpose coherently in a region of space The ratio of the maximum resultant intensity to the minimum resultant intensity is 4 1 If one of the waves has an amplitude A the amplitude of the other wave is A 4 A B 3 A C 2 A D An 0 2

1 Two ships A and B can establish mutual communication when they are not more than 50 km apart At midnight the ship B moving towards the north with a velocity 4 km h passes a location 80 km east of ship A that is moving with velocity 16 2 km h towards the northeast Find the time interval during which they were in communication

8 A uniformly charged ring of thickness t and surface charge density o is rotated about its axis with angular velocity w The magnetic field at the centre is foo 1 otw 3 2 otw It Mootw 2 4 None of these 2

ne a 1 5x 10 T c zero b 2 5 x 10 T d 3 x 10 T 44 A circular coil of wire consisting of 100 turns each of radius 9 cm carries a current of 0 4 A The magnitude of magnetic field at the centre of the coil is a 2 4 x 10 T c 2 79 x 10 T b 3 5 x 10 T d 3 x 10 T

3 If y a sin X 1 the dimensions of a is MOLTO 1 b 2 the unit of sin where y is in metre Then 1 1 is radian 3 the 4 the unit of a is metre dimensions of x are same as those of b

Consider the following replication fork formed by unwinding of DNA molecule 5 3 A C 5 Choose the option that indicates the direction in which replication is continuous A B B A B 3 C D

light ds of ively two e C is n the ction a All equal to 64 34 2 u 1 2u b What are moduli of acceleration vectors of the particles A B and C mmediately after the particle C is given velocity u 3u 3u 1 21 12u 6u d B 120 1 120 1 and u 1 4u and 120 u

In a transformer the number of turns in the primary and the secondary are 410 and 1230 respectively If the current in primary is 6A then that in the secondary coil is 1 2 A 2 18 A 3 12 A 4 1 A

m ne a c E E B B d E Ej B B 32 The energy of emergent protons in MeV from cyclotron having radius of its dees 1 8 m and applied magnetic field 0 7Tis massofproton 1 67x10 c 70 a 50 b 60 Which of the followin 33 d 76 35

move on any arbitrary path The operating magnetic field for accelerating protons in a cyclotron oscillator having frequency of 12 MHz is q 1 6 x 10 19 C m 1 67 x 10 kg and 1 MeV 1 6 x 10 131 a 0 69 T b 0 79 T c 0 59 T d 0 49 T c

1 Depends on the method of measurement 2 Does not depend on the method of measurement 3 Is more in SI system than in CGS system 4 Directly proportional to the fundamental units of mass length and time

2 The electrical potential on the surface of a uniformly charged sphere of radius r due to a charge 3 x 10 6 C on it is 500V The intensity of electric field on the surface of the sphere is in N C ni 1 10 2 200 3 between 10 and 20 4 5

A train of mass 4000 metric tons is moving with a velocity of 18 KMPH With the application of a force its velocities changes to 9 in 2 minutes If the power of the engine is 10 MW the value of 9 is in KMPH 1 72 2 90 3 36 4 54

78 A spring scale indicates a tension T in the right hand cable of the pulley system shown in the figure Neglecting the mass of the pulleys and the ignoring the friction between the cable and the pulley the mass M is equal to a 2T g b 3T g m c 4T g d T 1 e g

16 A circular metallic disc of radius R has a small circular cavity of radius r shown in figure On heating the System 1 R increases and r decreases 2 R decreases and r increases 3 Both R and r increases 4 Both R and r decreases

A rigid non conducting equilateral triangle of side is charged with charge q for segment AB A negative charge q is kept at vertex C A horizontal uniform electric field of strength E exists as shown The work done by electric field in rotating the frame about C such that BC becomes horizontal is A 91E B 3qlE 5 SqlE 7 C B E D 3qlE 4

20 A container has N molecules at absolute temperature T If the number o molecules is doubled but kinetic energy in the box remain the same as before the absolute temperature of the gas is 1 T 2 2 T 3 3T 4 4T

What mass in grams is needed to vibrate the string linear mass density is 0 024 g cm and produce a standing vave shown in the picture below The frequency of the vibrator is 139 Hz and the length of the string is 55 cm Enter only the numerical value and must be a whole number pulley LH mass vibrator

79 The orbital velocity of a satellite is given by the GM expression V V R h Earth R is the radius of the Earth and h is the height of the satellite from the surface of the Earth Explain the reasons why the geostationary satellite is not pos sible to set in orbit around the Earth at two different heights from the surface of the Earth 9 here M is the mass of the 80 A body is dropped from a height of 40 m from the surface of the Farth Its final l 28 m 5 1