Basic Physics Questions and Answers

6 Two students simultaneously start from the same place on a circular track and run for 2 min In this time one of them completes three and the other four revolutions Due to thick vegetation in a circular area as shown in the figure either of the boys can see only one third of the track at a time How long during their run do they remain visible to each other a 20 s c 80 s b 40 s d 160 s

F F and F represent three forces acting along the sides AB BC and AC respectively If the total torque about O is zero then the magnitude of Fis A F F B F F 2 F F

35 View in English Two particles of masses my and my are projected from the top of a tower The particle my is projected vertically downward with speed u and particle my is projected horizontally with some speed Th acceleration of contre of mass of the system is neglect air resistance 4 1 2 3 4 rect Answer g downward mig m m m2g m m Zaro downward downward V

5 Calculate the saturation thermionic current if 120 W is 2 applied to a thoriated tungsten filament of surface area 1 0 cm Assume that the surface radiates like a blackbody The required constants are 2 K q 2 6 eV k 8 62 10 A 3 10 Am and o 6 108 W m 2K 4 eV K

6 15 A particle of mass m is subjected to an attractive central force of magnitude k r k being a constant If at the instant when the particle is at an extreme position in its closed path at a distance a from the centre of the force its speed is k 2ma find the other extreme position Ane r a 1

An electric current is flowing in a very long pin as shown in the figure The value of magnetic flux density at point O will be 1 R 3 Po 2 2 T 1 Aal 4R 2 Jual 4TR Hal 4TR Hol TER 1

4 The constant A in the Richardson Dushman equation is 4 60 10 Am K2 for tungsten A tungsten cathode has a total surface area of 20 x 10 m and operates at 2000 K The work function of tungsten is 4 55 eV Calculate the electric current due to thermionic emission

The upper half of an inclined plane of inclination 0 is perfectly smooth while the lower half is rough A body starting from the rest at top comes back to rest at the bottom if the coefficient of friction for the lower half is given 1 sin e 2 cot 0 3 2 cos e 4 2 tane

53 Particle A moves along the line y 4 3 m with constant velocity of magnitude 2 0 m s and A B directed parallel to the positive x axis see figure Particle B starts at the origin with zero speed and constant acceleration of magnitude 4 0 m s at the same instant that the particle A passes the y axis The angle between a and the positive y axis that would result in a collision between these two particles should have a value equal to a 30 c 50 4 3 m b 45 d 60 10 AMU Med

A charged capacitor and an inductor are connected as shown in the drawing 778 C There is no resistance in the circuit As Section 23 4 discusses the electrical energy initially present in the charged capacitor then oscillates back and forth between the inductor and the capacitor The initial charge on the capacitor has a magnitude of q 3 00 pc The capacitance is C 3 30 F and the inductance is L 90 0 mH a What is the electrical energy stored initially by the charged capacitor Energy i 1 37 b Find the maximum current in the inductor A L 0000

The gros length of penstock supplying water from reservoir to the turbine is 400 m The diameter of the penstock is 1 m and velocity of water through penstock is 5 m s If coefficient of friction is 0 0098 the net head on the turbine would be nearly a 310m 200 m b 295 m d 150 m

73 Match the Column I with Column II Column I A B G 4 000000 000000 ww 000000 000000 M BOOBOD 000000 m p c A r d A p q C Column II T 2n s T 21 T 2n a A p B q C s D r B C p D q b A s m k k kjk B p C s D q B r C q D s 2m T 21 221 2 k m k k 77 78 79

72 Two identical springs of spring constant k are attached to a block of mass m and to fixed supports as shown in the figure The time period of oscillation is a 27 m k c 27 000000 oooooo b 2 m 2m 2k k the Column I with Column II m 2k d

2 The motor of an engine is rotating about its axis with an angular velocity of 100 rpm It comes to rest in 2015 s after being switched off Assuming constant angular deceleration What are the numbers of revolutions made by it before coming to rest c 32 6 d 15 6 a 12 5 el b 40 b

3 A boy takes 60 min to swim across a river if his goal is to minimize time and takes 180 min if his goal is to minimize to zero the distance that he is carried downstream In both these attempts the boy swims with the same speed relative to the river current Which of the following statements can be true a He can swim relative to water faster than the river current b He cannot swim relative to water faster than the river current c If width of the river is 3 2 km speed of river current is 4 km h d If he crosses a 3 2 km wide river in 60 2 min he will be carried 2 km downstream

c d 41 The piston in the cylinder head of a locomot has a stroke of 6 m If the piston executing simple harmonic motion with an angular frequency d 200 rad min its maximum speed is a 5 ms b 10 ms c 15 ms d 20 mg 42 A particle executing SHM according to the equation

6 16 If the radius of the earth shrinks by one percent its mass remaining the same by what per cent will the acceleration due to gravity on its surface change Ans Will increase by 2

An ideal gas equation can be written as P where P and Mo are respectively mass density mass of the gas INCORRECT number density molar mass mass density molar mass CORRECT ANSWER number density mass of the gas

A horizontal jet of water with its cross sectional area of 0 0028 m hits a fixed vertical plate with a velocity of 5 m s After impact the jet splits symmetrically in a plane parallel to the plane of the plate The force of impact in N of the jet on the plate is a 90 c 70 b 80 d 60

A cubical solid aluminium bulk modulus V 70 GPa block has an edge length of 1 m on th dv surface of the earth It is kept on the floor of a 5 km deep ocean Taking the average density of water an the acceleration due to gravity to be 103 kg m and 10 ms 2 respectively the change in the edge lengt of the block in mm is 5 0 24 B P dv P de dv V B 3 de 0 238 x 10 3 d 0 238 mm 0 24 P PIB B 3d P 10m 103 kg x x5x10 m 70x10 1m Em 3

In water when pressure force increases cross sectional area decrease then viscosity decrease so velocity of water increase And without water in any liquid when pressure force increases cross sectional area decrease so viscosity increase then velocity decrease this is totally opposite to Bernoulli theorem 8 19 PM

Two tangent galvanometers A and B connected in series to a d c source have their number of turns in the ratio 1 3 and diameters in the ratio 1 3 of their coils which is correct for reduction factor and deflection of both galvanometers A B C D K KB 0 0 A B K K 0A 0B KA KB 0 0B K K 0 0 A A B

A train travels with a speed of 60 km h from station A to station B and then comes back with a speed 80 km h from station B to station A Find i the average speed and ii the average velocity Ans i 68 57 km h ii zero of train

A parallel plate capacitor of capacitance 20 F is being charged by a voltage source whose potential is changing at the rate of 3 V s The conduction current through the connecting wires and the displacement current through the plates of the capacitor would be respectively NEET 2019 ont 1 Zero 60 A 2 60 A 60 A 3 60 A zero 4 Zero zero Q CV do dt c du du

A glass plate 3 30 mm thick with an index of refraction of 1 65 is placed between a point source of light with wavelength 560 nm in vacuum and a screen The distance from source to screen is 2 90 cm Part A How many wavelengths are there between the source and the screen AEO

A straight horizontal stretch of copper wire carries a current i 30 A The linear mass density of the wire is 45 g m What is the magnitude of the magnetic field needed to float the wire that is to be balance its weight 1 147 G 2 441 G 4 0 G 3 14 7 G

a c 3 m 6 m s 6 A particle executes SHM of period 12 s After two seconds it passes through the centre of oscillation the velocity is found to be 3 142 cms The amplitude of oscillations is a 6 cm b 3 cm c 24 cm d 12 cm imple harmonic motion with

makes an angle of 45 0 degrees with the positive x axis Vector B also has a magnitude of 8 units and is directed along the negative x axis The magnitude of A B is TRQ B 8 Select one OA 4 65 OB None O C 14 78 D 8 22 4 2 45 4 2

1 a What would have to be the self inductance of a solenoid for it to store 10 0 J of energy when a 1 50 A current runs through it b If this solenoid s cross sectional diameter is 4 00 cm and if you could wrap its coils to a density of 10 coils mm how long would the solenoid be See Problem 34 Is this a realistic length for ordinary

A car travels at 15 m s for 10 s It then speeds up with a constant acceleration of 2 0 m s2 for s The average speed of the car is 15 h 2 5 m s 2 4 O m s 86

A magnetic needle is made to vibrate in uniform field H then its time period is T If it vibrates in the field of intensity 4H its time period will be a 2T b T 2 c 2 T d T 10

6 44 A particle is projected from earth surface with a velocity in upward direction where R is the radius of earth Find the velocity of particle when it is at half its maximum height 4gR V 3

A container with 1 kg of water in it is kept in sunlight which causes the water to get warmer than the surroundings The average energy per unit time per unit area received due to the sunlight is 700 Wm and it is absorbed by the water over an effective area of 0 05 m Assuming that the heat loss from the water to the surroundings is governed by Newton s law of cooling the difference in C in the temperature of water and the surroundings after a long time will be Ignore effect of the container and take constant for Newton s law of cooling 0 001 s 1 Heat capacity of water 4200 J kg K 8 33 P 700 x 0 05 35 watts P Pr 35 eGA4T0 AT K 4eGAT mc AT 0 0001 4e AT0 0 001 x mC 4 2 from equation 1 35 50 25 8 33

d The acceleration of the particle is maximum a 35 Displacement versus time curve for a particle executing SHM is as shown in figure Displacement Time At what points the velocity of the particle is zero a A C E b B D F c A D F d C E F

neet prep Mini Test 1 A neutral point is obtained at the centre of a vertica circular coil carrying current The angle between the plane of the coil and the magnetic meridian is

53 A uniform disc of radius R lies in x y plane with its centre at origin Its moment of inertia about z axis is equal to its moment of inertia about line y x c The valne of c is R 2 b R 2 c R 4 d R A uniform rod of mass mand length 2a lies at root

The amount of work done in increasing the voltage across the plates of the capacitor from 5 V to 10 V is W The work done in increasing it from 10 V to 15 V will be A W Your Answer B 0 6 W C 1 25 W D 1 67 W

21 If a uniformly charged non conducting spherical body is rotating with angular velocity w the charge and mass of body are q and m respectively then the magnetic moment is 1 1 qr w 1 3 qr w 2 2 2 5 qr w 2 4 qr w

a 40 A block of mass m is attached to a spring of sp constant k is free to oscillate with angular veloce in a horizontal plane without friction or dam It is pulled to a distance x and pushed toward centre with a velocity v at time t 0 The ampl of oscillations in terms of 0 x and vis b x c 00 N ON d N W

The electrostatic potential existing in space is given by I xy yz zx volts where x y and z are in metres The angle made by electric field Eat 2 m 2 m 2 m with positive x axis is a Then O cosa O cosa O sin a O tana 1 1

2 The relations amongst the three elements of Earth s magnetic field namely horizontal component H vertical 3 component V and dip angle are B total magnetic field 4 1 V Bg tan 6 H BE 2 V BE sind H BE cos 3 V BE cos 8 H Bg sin d 4 V Bg H Bg tand 20 Ju 24 Lo ma 1 2 3

Electric potential energy possessed by a charge q place at the equatorial position of an electric dipole P 2qa at a distance r from the centre of the dipole is O Zero O kq a kq CT3 2 kq a

hich of the following operations related to an electrical phenomenon does the mass of a body decrease strictly speaking if the mass of an electron or a proton is not neglected The body has positive charge by rubbing with another body A body s mass never changes by electrical phenomenon The body has negative charge by rubbing with another body The body is polarized by another charged body without being in with it

Select the correct statement If electric field is zero at a certain point then potential should be zero at that point If electric field is not zero at a certain point then potential should not be zero at that point If potential is zero at a certain point then electric field should be zero at that point If potential is zero at a certain point then electric field at that point may or may not be zero

A mass of 1kg is acted on by a restoring force with force constant 4 N m and a resisting force with damping coefficient 2N s m Write down the equation of motion in one dimension Find whether the motion is periodic or oscillatory Find the value of the restoring force which will make the motion critically damped

3vx L 3x A mvx A C D From angular momentum conservation ML2 mx 0 3 B 3vx L 3x For maximum angular velocity doo 0 dx d L dx x 3x 0 3v 12vx L 12x L 3 0 X 3 C XM 1 3 D OM V 2L

Two coils have a mutual inductance of 5 mH Current changes in the first coil according to the equation II cos wt where Io 10 A and w 100 rad s Maximum value of e m f induced in the second coil is 1 5 volt 2 2 volt 3 4m volt T volt

A 1 5kg block is initially at rest on a horizontal frictionless surface A horizontal A force F 4 x i is applied on the block Initial position of the block is at x 0 The maximum kinetic energy of the block between x 0 and x 2m is 1 2 331 2 8 67 J 3 5 33 J 4 6 67 J

2 A thin convex lens having focal length 20 cm is cu into two parts 1 mm above the principle axis The lower portion is placed with optical centre at origin and upper portion at 90 0 as shown in the figure A point object is placed at 30 0 Find the magnitude of y coordinates in mm of the image Assuming paraxial ray approximation to remain valid 30 0 1 mm 0 0 30cm 90cm 90 0

3 A capacitor of capacity C 1 F is charged to a potential of 100 V The charging battery is then removed and it is connected to another capacitor of capacity C 2 F One plate of C is earthed as shown in figure The charges on C and C in steady state will be a 50 C 50 C 100 c C n 200 2 C HH C C HH b100 C zero d zero zero