# Basic Physics Questions and Answers Physics
Basic Physics
A cord is wound over the rim of a flywheel of mass 20 kg and radius 25 cm A mass 2 5 kg attached to the cord is allowed to fall under gravity The angular acceleration of the flywheel is a 25 rad s c 10 rad s b 20 rad s d 5 rad s Physics
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17 A train is moving with a velocity of 30 km h 1 due East and a car is moving with a velocity of 40 km h due North What is the velocity of car as appears to a passenger in the train Physics
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1 A positively charged particle projected towards east is deflected towards north by a magnetic field The field may be a towards west c upward b towards south d downward horizontal circle on Physics
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50 0 kg of N g and 10 0 kg of H g are mixed to produce NH3 g Calculate the moles of NH g formed Identify the limiting reagent in the production of NH3 in this situation Hint N g 3H g 2NH3 g to form water Find out the mass of water obtained Which Physics
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The power of spectacles lens required for a person is 5 dioptre when separation between spectacles and eye is 2 cm What will be the power of contact lens required by him 1 5 25 D 3 3 2 D 2 4 75 D 4 5 75 D Physics
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21 A glass vessel contains air at 60 C To what temperature must it be heated to expel one third of the air the pressure remaining con stant Neglect the expansion of the vessel 1 127 C 3 327 C 2 226 5 C 4 427 C Physics
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If two vectors A 1 3 5k and A 1 31 ak are equal then the value of a is a 5 b 5 a 2 Physics
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A rough wedge of slant length 5 m is kept as shown in the figure Find the height h if the block of weight 10N just starts to slip in the given figure The coefficient of friction between the block 1 the wedge is Physics
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If a semiconductor has an intrinsic carrier concentration of 141x 10 6 m when doped with 1021 m phosphorous atoms then the concentration 3 of holes m at room temperature will be a 2 x 10 1 b 2 x 10 1 2009 c 1 41x 10 0 d 141x10 6 Physics
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169 Find the torque about the origin when a force of 31 N acts on a particle whose position vector is C for 2km 2 3 4 61 Nm 6 Nm 6 i Nm A 6k Nm i j k 3 2 6 0 1 0 0 kjent Physics
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Calculate the molarity of NaOH in the solution prepared by dissolving its 4 g in enough water to form 250 mL of the solution Physics
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Kinetic energy of the system city of centre of mass of two particles is v and the sum of the masses of two particles is m A will be equal to mv C will be greater than or equal to mv Ball 1 B will always be less than 1 mv D will always be greater than mv Physics
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Two particles 1 and 2 are moving with velocities v 41 31 m s and v bi j m s respectively The position vectors of the particles at time t 0 are 51 2 m and 2 41 43 m If they collide at t 3s the value of bis A 10 3 B 5 C 1 D 7 Physics
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ass X Three boys A B and C are situated at the vertices of an equilateral triangle of side d at t 0 Each of the boy moves with constant speed v A always moves towards B B towards C and C towards A At what time an where they meet each other troid of the triangle Approaching Physics
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Speed of a boat in standing water is 9kmph and the speed of the stream is 1 5kmph A man rows to a place at a distance of 105km and comes back to the starting point Find the total time taken by him Physics
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Which one of the following represents a wave a y A sin oot kx b y A cos at bx c c y A sin kx d y A sin of 1994 Physics
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The diagram shows a solenoid carrying time varying current I It I is constant On the axis of this solenoid a conducting ring is being placed as shown in figure The mutual inductance of the ring and the solenoid is M and self inductance of the ring is L If the resistance of the ring is R then the maximum current which can flow through the ring is A 2M L Io MI B e ring C 2M L Io R D M L Io R Physics
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8 An airplane pilot wants to fly from city A to city B which is 1000 km due north of city A The speed of the plane in still air is 500 km hr The pilot neglects the effect of the wind and directs his plane due north and 2 hours later find himself 300 km due north east of city B The wind velocity is B 106 km hr at 45 N of E D 106 km hr at 45 N of W A 150 km hr at 45 N of E C 150 km he at 45 N of W aragraph for question nos 39 to 40 An obsencork Physics
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A B C D Column I Particles are projected at same speed from same point on level ground such that their range is same Particles are projected from same point on ground such that maximum height reached is same Particles are projected horizontally from same point at a height with different initial velocities Particle are projected from the same point at a height with same initial speed direction of velocity makes equal angle with horizontal one below and the other above horizontal Column II P Q R S Time of flight will be same Speed just before reaching ground will be same Vertical component of velocity just before reaching ground will be same Minimum kinetic energy durir the flight will be equal Physics
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In an undershot water wheel the cross sectional area a 0 1 m of the stream is striking the series of radial flat vanes of the wheel The velocity of stream is 6 m s The velocity of vanes is 3 m s If the power supplied by jet in watts is 2700K find K Water jet U Physics
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A metal rod OA of mass m length r is kept rotating with a constant angular speed o in a vertical plane about a horizontal axis at the end O The free end A is arranged to slide without friction along a fixed conducting circular ring in the same plane as that of rotation A uniform constant magnetic induction B is applied perpendicular into the plane of rotation as shown in figure An inductor L and an external resistance R are connected through a switch S between the point O a point C on the ring to form an electrical circuit Neglect the resistance of the ring and the rod Initially the switch is open a What is the induced emf across the terminals of the switch b i Obtain an expression for the current as a function of time after switch S is closed S R ii Obtain the time dependence of the torque required to maintain b the constant angular speed given that the rod OA was along the positive X axis at t 0 X X mmmm L X y 20 0 AXX Physics
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There are 5 different boxes and 7 different balls The number of ways in which these balls can be distributed so that box 2 and box 4 contain 1 ball each and at least 1 box is empty is N The order of putting the balls in the boxes is not considered The digit in the hundredth s place of N is equal to Physics
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In a p n junction diode change in temperature due to heating a does not affect resistance of p n junctio b affects only forward resistance c affects only reverse resistance d affects the overall V characteristics of p n junction Physics
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iv The magnitude of area of the parallelogram formed by the adjacent sides of vectors A 31 21 a nd 3 21 2k is Sol Physics
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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 Physics
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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 Physics
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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 Physics
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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 Physics
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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 Physics
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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 Physics
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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 Physics
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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 Physics
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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 Physics
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A proton and an alpha particle are accelerated through the same potential difference The rati of wavelengths associated with proton and alph particle respectively is 212 1 3 2 5 1 44 1 Physics
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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 Physics
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6 The numbers 2 745 and 2 735 on rounding off to 3 significant figures will give a 2 75 and 2 74 c 2 75 and 2 73 b 2 74 and 2 73 d 2 74 and 2 74 Physics
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Two sinusoidal currents are given by the equation 50 sin at i 25 sin cot The phase difference between them is degrees Select one O a 75 O b 45 c 30 d 15 Physics
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int of as a resultant reaction and Applied force frictional force O normal reaction frictional force applied force the weight of the bo normal reaction the weight of the Previous Save Nex To be reviewed la Physics
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1 4 3 2 3 4 A number of small drops of mercury adiabatically 1 increase 2 remain same spherical 3 16 9 4 64 27 coalesce to form a single drop The temperature of the drop 3 decrease 4 depend on size Physics
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10 A massless rod of length is suspended by two identical string AB and CD of equal length A block of mass 10 Kg is suspended from point P such that DP is equal to X It is also observed that the frequency of 1st harmonic in AB is equal to 3rd harmonic frequency in CD Then find X C 10 l A B 10 Kg D 9l 10 AP Physics
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Water is moving with a speed of 5 18 ms through a pipe with a cross sectional area of 4 20 cm The water wat gradually descends 9 66 m as the pipe increase in area to 7 60 cm The speed of flow at the lower level is 3 3 82 ms 4 2 86 ms 2 5 7 ms 1 3 0 ms l Physics
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2 What is a Rectifier Explain in detail two types of circuits for a full wave rectifier Also calculate rectifier efficiency and ripple factor for a full wave rectifier Physics
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33 In the shown arrangement if f f and T be the frictional forces on 2 kg block 3kg block tension in the string respectively then their values are P 0 1 1N 2kg 1 2 N 6 N 3 2 N 2 2 N 6N ON 3kg 8N M 0 2 f 0 2 3 1 N6 N 2 N 4 data insufficient to calculate the required values Physics
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Rain pouring down at an angle a with the vertical has a speed of 10 ms A girl runs against the rain with a speed of 8 ms and sees that the rain makes an angle with the vertical then relation between a and B is Physics
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1 1 2 3 273 A non planer loop of conducting wire carrying a current I is placed as shown in the figure Each of the straight sections of the loop is of length 2a The magnetic field due to this loop at the point P a 0 a points in the direction 1 k L 2a 2 j k i 3 i j k 1 85 7 SX100 fk i k B 4000X SY 100 Physics
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Figure shows a circuit that contains three identical resistors with resistance R 9 0 Q each two identical inductors with induc tance L 2 0 mH each and an ideal battery with emf 18 V The current i through the battery just after the switch closed is 0000 a 0 2 A c 0 ampere R R L b 2 A d 2 mA NEET 2017 Physics
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Two block A and B placed on a plane surface as shown in the figure The mass of block A is 100 kg and that of block B is 200 kg Block A is tied to a stand and block B is pulled by a force F If the coefficient of friction between the surfaces of A and B is 0 2 and the coefficient of friction between B and the plane is 0 3 then for the motion of B the minimum value of F will be 1050 N A B 3 900 N 4 1100 N Physics
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A box A is lying on the horizontal floor of the compartment of a train running along horizontal rails from left to right At time t it decelerates Then the reaction R by the floor on the box is given best by AR 1 A floor aet 2 R A floor e 3 TI A 4 floor ar floor hogins to slide when the length of hanging part is Physics
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A body is at rest at x 0 At t 0 it starts moving in the positive x direction with a constant acceleration At the same instant another body passes through x 0 moving in the positive x direction with a constant speed The position of the first body is given by x1 t after time t and that of second body by x2 t after the same time interval Which of the following graphs correctly describes x1 x2 as a function of time t AIEEE 2008 LL 1 x x 3 O x x LL 4 X X x x Physics
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5 A car is moving on a straight road The velocity the car varies with time as shown in the figure Initially at t 0 the car was at x 0 where x is position of the car at any time t Find acceleration of car at time t 15 sec and t 55 sec v m s 8 4 10 20 30 1 0 5 m s 2 3 0 0 4 m s 50 60 70 t sec 2 0 0 4 m s 4 0 0 2 m s