Physics Questions

If an electrion is placed in a uniform electric field then the electron will 1 experience no force 2 moving with constant velocity in the direction of the filed 3 move with constant velocity in the direction opposite to the field 4 accelerate in direction opposite to field

Which one of the following statements is not true about Newton s second law of motion F m a The second law of motion is consistent with the first law b The second law of motion is a vector law c The second law of motion is applicable to a single point particle d The second law of motion is not a local law

The length of potentiometer wire is L A cell of emf e is balanced at a length from the positive End of the wire Assuming there is no contribution in resistance from any part of the circuit except the potentiometer wire the balancing length fa the same cell if the length of the wire is increased by is 2 2L 1 2 1 20 15 Check all that apply A B C 3L 15 31 3 10 2L 4 2 4 5 4 point L

8 Two identical long conducting wires AOB and COD are placed at right angle to each other such that one is above the other and O is their common point The wires carry and 1 currents respectively Point P is lying at distance d from O along a direction perpendicular to the plane containing the wires The magnetic field at the point P will be CBSE AIPMT 2014 Ho 4 a Ho 2nd c H0 1 12 2nd b Ho d Inti 1 1 2nd Ho 1 12 1 2nd

A bullet moving with a uniform velocity v stops suddenly after hitting the target and the whole mass melts to m specific heat S initial temperature 25 C melting point 475 C and the latent heat L Then v is given by 1 mv 1 mL mS 475 25 J 2 mS 475 25 mL 3 mS 475 25 mL 4 mS 475 25 ml JE mv 2J mv mv

Transfer characteristics output voltage V vs input voltage V for a base biased transistor in CE configuration is as shown in the figure For using transistor as a switch it is used I Vol II III a in region III b both in region I and III c in region II d in region I The figura 2012

a 26 8 b 20 c 6 25 d 12 5 NEET 2018 At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from the Earth s atmosphere Given Mass of oxygen molecule m 2 76 x 10 26 kg Boltzmann s constant kg 1 38 x 10 23 J K B a 2 508 x 104 K c 5 016 104 K b 8 360 x 10 K d 1 254 x 10 K NEET 2018 un eq of a 12 T t

Consider the circuit shown in the figure Capacitors A and B each have capacitance C 2 F The plates of capacitor A are shorted using a wire of resistance R 1 2 while the left plate of capacitor B is given an initial charge Q 4 C The switch is closed at a time t 0 What will be the initial current in ampere drawn from the battery immediately after the switch is closed Ans 7 A C www R H www R E 4Q C

8 The displacement of a particle moving along the x axis is given by equation x 2t 21t 60t 6 The possible acceleration of the particle when its velocity is zero is NEE 2016 18m s 2 30 m s 4 9m s F 3 9m s2

M M 18 Calculate the tensions T T and T3 in the three threads shown in the following figure All threads are massless g 10 m s T 137 T 5 T 4 kg 1 30 N 40 N 50 N 2 50 N 30 N 40 N 3 35 N 45 N 40 N 4 30 N 50 N 40 N 19 A heavy block of mass M hangs in equilibrium at the end of a rope of mass m and length connected to a

18 Shift 1 An active nucleus decays to one third 13 in 20 Hrs The fraction of original activity re maining after 80 Hrs is 1 a b 16 1 c d 36 1 812201 1 54

47 If 0 is angle between the velocity and acceleration of a particle moving on a circular path with decreasing speed then 1 0 90 2 0 0 90 3 90 0 180 A 180 1

D A certain radioactive element has a half life of 20 years If we have a block with 10 g of the element in it after how many years will there be just 2 5 g of the element in the block a 80 years 40 years c 100 years 60 years b d 1995 2001

Two identically charged sphere are suspended by string of equal length The strings make an angle of 30 with each other When suspended in a liquid of density 0 8 g cc the angle remains same What is the dielectric constant of liquid Density of sphere 1 6 g cc 1 1 2 30 15 mg 3 3 F 4 4

2 A car moving at 40 km h is to be stopped by applying brakes in the next 4 0 m If the car weighs 2000 kg what average force must be applied on it

of four identical resistances should be used to draw maximum energy from a cell of voltage V 15 11x 1X4 B 38 www www www www P v RUI Parallel 3 15 3 x 11 33 45 15x 12

A conductor of length 10cm carrying current 1200A Find the magnetic field at a distance 2cm along the axis from its centre

4 Time period of a simple pendulum of length is T and time period of uniform rod of same length l pivoted about one end and oscillating in a vertical plane is T2 Amplitude of oscillations in both the cases is small then T 21 1 3 3 3 T is T 2 2 1 4 13

A block of mass 10 kg is placed on a long trolley The coefficient of friction between the block and trolley is 0 2 The trolley accelerates from rest with 0 5 m s for 20 s then what is the friction force 1 20 N 2 100 N 3 5 N 4 10 N

An air core parallel plate capacitor has capacitance Co and separation between its plates is do It is given a charge Qo and connected to a bulb of resistance R through a switch S The switch is closed at time t 0 and the separation between the capacitor plate is changed as d for 0 t 1 second For t 1 do 1 t do second the plate separation is held fixed at d 2 Find charge on the capacitor at t 1 second is Find charge on the capacitor as a time t 1 second is HH J www R S

5 A body is revoluing around sun with closest of 8 x 10 0 m and farthest distance of distance 1 x 10 2 m Time period of the body will be The mass of sun is 2 x 1030 kg 1 6 85 year 2 3 6 year 3 10 8 year 4 12 year

Mark the correct statement s A when a sound wave strikes a wall the compression pulse is reflected as compression pulse B when a sound wave strikes a wall the compression pulse is reflected as rarefaction pulse C when a sound wave is coming out after passing through a narrow pipe then reflection would be there at open end D when a sound wave is coming out after passing through a narrow pipe then compression pulse is reflected as rare fraction pulse

1 A fix amount of nitrogen gas 1 mole is taken and is subjected to pressure and temperature variation The experiment is performed at high pressure as well as high temperatures The results obtained are shown in the figures The correct variation of PV RT with P will be exhibited by UPSEAT 2001 4 PV RT a 4 2 0 1 0 3 2 b 3 1 P 100 200 400 600

2 A 100 m long train crosses a man travelling at 5 kmh opposite direction in 7 2 s then the velocity of train is a 40 ms b 25 ms c 20 ms 1 d 45 ms

If the instantaneous velocity of a particle projected as shown in figure is given by v ai b ct j where a b and c are positive constants the range on the horizontal plane will be y 1 2ab c 3 ac b 2 ab c 4 a 2bc X

Two coherent plane light waves of equal amplitude makes a small angle a 1 with each other They fall almost normally on a screen If is the wavelength of light waves the fringe width Ax of interference patterns of the two sets of waves on the screen is a c 5 8 2 3 20 6 d a

An electron is projected with a velocity 2 x 105 m s at an angle 30 with a uniform magnetic field of 0 4 T Find radius of curvature of path of the electron A proton of mass x 10 27 1

c 0 tan Three particles A B and C are thrown from the top of a tower with the same speed A is thrown up B is thrown down and C is horizontally They hit the ground with speeds VA VB and Odisha JEE 2005 DCE 2006 Vc respectively a VA VB Vc b V VB Vc c VB VC VA d VA VB Vc tind to a string of length 1 and is revolved in a

There is an isolated planet having mass 2M and radius 2R where M and R are the mass and radius of the earth A simple pendulum having mass m and length 2R is made to small oscillations on the planet Find the time period of SHM of pendulum in second take 3 00 g 10 m s 2 1 41

7 Two blocks are connected to an ideal spring of stiffness 200 N m At a certain and the instantaneous blocks are moving in opposite directions with speeds 4 ms and 6 ms is increasing is elongation of the spring is 10 cm The rate at which the spring energy 2 kx d 100 J s 0 000 TL ne two

Size of a Molecule To measure a very small size like that of a molecule 108 m to 10 10 m we have to adopt special methods We cannot use a screw gauge or similar instruments Even a microscope has certain limitations An optical microscope uses visible light to look at the system under investigation As light has wave like features the resolution to which an optical microscope can be used is the wavelength of light A detailed explanation can be found in the Class XII Physics textbook For visible light the range of wavelengths is from about 4000 to 7000 1 10 0 m Hence an optical 1 angstrom microscope cannot resolve particles with sizes smaller than this Instead of visible light we can use an electron beam Electron beams can be focussed by properly designed electric and magnetic fields The resolution of such an electron microscope is limited finally by the fact that electrons can also behave as waves You will learn more about this in class XII The wavelength of an electron can be as small as a fraction of an angstrom Such electron microscopes with a resolution of 0 6 have been built They can almost resolve atoms and molecules in a material In recent times tunnelling microscopy has been developed in which again the limit of resolution is better than an angstrom It is possible to estimate the sizes of molecules A simple method for estimating the molecular size of oleic acid is given below Oleic acid is a soapy liquid with large molecular size of the order of 109 m The idea is to first form mono molecular layer of oleic acid on water surface We dissolve 1 cm of oleic acid in alcohol to make a solution of 20 cm Then we take 1 cm

2 A pair of coils of turns n and n are kept close together Current passing through the first is reducing at rate r and e m f 3 mV is developed across the other coil If the second coil carries current which is then reduced at the rate 2r the emf produced across the first coil will be 1 6n mV n 3 6 mV 2 6n2 mV n 3 4 mV

A lens has a power of 5D in air What will be its power if it is completely immersed in water Given 3 oHg 1 4 2 0H 3 2 5 3 3 1D 2 4 MIN OTO D

Velocity v of a particle moving along x axis as a function of time is given by v 2t m s Initially the particle is to the right of the origin and 2 m away from it Find the position distance from origin of the particle after first 3 s a 5 m dr frat 3 b 7m fy Serd 0 m v ms 30 O t 60 A t B t s

5 Two thin concentric hollow conducting spheres of radii R and R bear charges Q and Q respectively If R R then the potential of a point at a distance r from the centre R r R is 1 Q Q r 1 ATEO 4180 1 Q 2 1 2 4E0 4 AC Q Q r R R Q

At NTP water boils at 100 C Deep down a mine water will boil at a temperature B 100 C 100 C Correct Answer 100 C

A mercury manometer figure 24 W1 consists of two unequal arms of equal cross section 1 cm and lengths 100 cm and 50 cm The two open ends are sealed with air in the tube at a pressure of 80 cm of mercury Some amount of mercury is now introduced in the manometer through the stopcock connected to it If mercury rises in the shorter tube to a length 10 cm in steady state find the length of the mercury column risen in the longer tube 10 cm 05 locm

A particle moves along a x axis according to given function x t 10 t 10t Find the average velocity of particle in time interval from t 0 to t t 10 seconds A zero B 5 m s C 5 m s D none of these

11 cc of water at its boiling point 100 C absorbs 540 cal of heat to become steam with a volume of 1671 cc If the atmospheric pressure is 1 013 x 105 Nm 2 the energy spent in cal to overcome molecular attractive forces is nearly mechanical equivalent of heat 4 2 J cal b 500 dibs c 40 a 540 d zero

0 75Gm R from the A missile is launched at an angle of 60 to the vertical with a velocity surface of the earth Neglecting air resistance find the maximum height reached by the missile from the surface of the earth me mass of the earth Re radius of the earth

ody is allowed to roll down inclined plane Th acceleration of centre of mass of body will depend 1 Mass of the body X 2 Radius of the body 3 Distribution and mass on the body 4 All of these az asu gsi 1 1 F

A ball strikes a wall with a velocity u at an angle 0 with the normal to the wall surface and rebounds from it at an angle with the surface Then 1 0 3 90 if the wall is smooth 2 If the wall is smooth coefficient of restitution tan B cot 3 If wall is smooth coefficient of restitution tan cot

A very long cylinder is carrying a current lo distributed uniformly over its cross section area as shown in the figure Find the value of fB de along the path AB from A to B shown in the figure O is the centre of the cross section of the cylinder and direction of current is in to the plane of the paper A Holo Holo 6 C A B B 600 Holo 6 D Can t be determined 0

stration 5 2 Assume that if the shear stress in steel exceeds about 4 00 x 108 N m the steel reptures Determine the shearing force necessary to a shear a steel bolt 1 00 cm in diameter and b punch a 1 00 cm diameter hole in a steel plate 0 500 cm thick

The value of magnetic field at O is 1 2 1 Zero Hol 2 2a 3 1 Hoi 4 none of these a a 0 vi 2

For any 81x Let a1 a2 a3 be a sequence of real numbers such that lim an real number x define an integer valued function f x as the smallest positive integer n for which an 2x Then for any integer n 1 and any real number x A f an n and af x x C f an n and af r 2x B f an n and af x x D f an n and af x x

The graph shows position as a func tion of time for two trains running on parallel tracks Which statement is true Position A B Time a At time tg both trains have the same velocity tB b Both trains have the same velocity at some time after tB c Both trains have the same velocity at some time be fore tp d Somewhere on the graph both trains have the same

25 The successive frequencies of standing waves setup in an organ pipe are 150 Hz 225 Hz 300 Hz then frequency of 10th harmonics is 1 1500 Hz 2 750 Hz 3 450 Hz 4 600 Hz 31

A current of magnitude 1000 005 mA is entering and simultaneously a current of 1000mA is leaving a metallic sphere of radius 20 cm Find the time at which potential of sphere becomes 1 kV 40 1 ms 2 40 ms 3 9 ms 4 10 ms 9

3 A tuning fork A produces 3 beats per second with tuning fork B On loading tuning fork B with wax beat frequency remains unchanged If frequency of tuning fork A is 343 Hz then frequency of tuning fork Bis