Basic Physics Questions and Answers

v A piece of gold weighing 36 g in air weighs only 34 g in water If in this piece some copper is mixed with gold find the amount of copper in it Specific gravity of gold is 19 3 and that of copper is 8 9 2 225 gl whe hei 8 t g

1 The mean free path of an ideal gas in a close container remains same if 1 Temperature increases 2 Temperature decreases Temperature remains constant All of these

3 100 J 4 150 J 20 A particle is moving along a circular path of radius 10 m with a uniform speed 10 m s What will be the average acceleration when the particle completes half revolution 10 1 m s 3 10 m s 2 20 m s 4 Zero

A car moving at a speed of 36 km hr is taking a turn on a circular road of radius 50 m A small wooden plate is kept on the seat with its plane perpendicular to the radius of the circular road figure A small block of mass 100g is kept on the seat which rests against the plate The friction coefficient between the block and the plate is u 1 3 0 58 a Find the normal contact force exerted by the plate on the block b The plate is slowly turned so that the angle between the normal to the plate and the radius of the road slowly increases Find the angle at which the block will just start sliding on the plate O

52 The structure of a water molecules is shown in th figure What is the distance of the centre of mass c the molecule from the centre of the oxygen atom O 0 96 10 10 m H A 6 4 10 m C 4 6 x 10 10 m 104 0 96 10 10 m H B 6 4 x 10 1 m D 4 6 x 10 12 m

viii A uniform rod AB 4 m long and weighing 12 kg is supported at end 4 with a 6 kg lead weight at B The rod floats as shown in the figure 7 17 with one half to its length submerged The buoyant force on the lead mass is negligible as it is of negligible volume Find the tension in the cord and the total volume of the rod Take g 10 m s Figure 7 17

ix Water stands at a depth H behind the vertical face of a dam and exerts a certain resultant horizontal force on the dam tending to slide it along its foundation and a certain torque tending to overturn the dam about the point O If the total width of the dam is L find a the total horizontal force b the total torque about O and c moment arm of the resultant horizontal force about the line through O O nt r er perumay besok 1 a og H h og H c H

ii Figure 7 34 shows a L shaped tube in which a liquid of density p is filled Find with what acceleration the tube is accelerated toward right so that no liquid will fall out of the tube h a 1 Figure 7 34 is tha pr W 1 h C

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole I AIPMT Prelims 2012 1 Will stay in north south direction only 2 Will stay in east west direction only 3 Will become rigid showing no movement 4 Will stary in any position

between the plates 14 Three capacitors of equal capacitance when connected in series have a net capacitance C 1 and when connected in parallel have net capacitance C 2 What is the ratio of capacitance C1 and C2

3 2 5 x 10 5 cm 4 1 25 x 105 cm 41 A particle of mass m moving eastward with a speed V collides with another particle of the same mass moving northward with the same speed V The two particles stick to each other with collision The new particle of mass 2m will move in the North East direction with a velocity 1 V 3 2 4 V 2 2

The photoelectric threshold frequency of a metal is v When light of frequency 4v is incident on the metal the maximum kinetic energy of the emitted photoelectrons is 1 4 hv 2 3 hv 5

42 Two cells of emf E and E are joined in series and the balancing length of the potentiometer wire is 600 cm If the terminals of E are reversed E E the balancing length obtained is 150 cm The ratio of E E will be 1 5 3 2 3 2 3 1 4

0 A stone of mass m moves with a speed v and gets all of a sudden splitted into two parts If the piece of mass m remains stationary the speed of the other piece shall be A C m v m m m v m m B D m2v m m miv m

Test 3 Code A A Carnot engine takes in 3000 kcal of heat from a reservoir at 627 C and gives it to the sink at 27 C The work done by the engine is 1 4 2 10 J 2 8 4 x 105 J 3 16 8 x 106 J

D The beaker completely filled with water is kept in an evacuated chamber If the pressure at bottom of beaker is P then pressure at half depth of beaker is 1 2P 3 PIN 2 4 4P

4 107 8 12k N m 36 Fig shows a capillary tube dipped in water If P is the atmospheric pressure P the pressure at x and P the pressure at y then T JEE FO 1 P P P 3 P P P P 2 P P P P 4 P P P P

9 A metallic sphere the coefficient of linear expansion c 2 x 10 per C of radius 10 cm is heated at the rate of 2 C per second Its volume will increase at the initial rate of 1 6 x 10 6 cm s 3 16m x 10 2 12 x 10 6 cm s 4 8m x 10 cm s cm s

3 30 cm 4 40 cm 5 In a Young s double slit experiment let be the fringe width and I be the intensity of the central bright fringe At a distance x from the central bright fringe the intensity will be 1 1 cos 2 1 cos 3 cos

capacitor 22 A tuning fork of frequency 500 Hz is sounded on a resonance tube The first and second resonances are obtained at 17 cm and 51 cm The velocity of sound is neglect end corrections 1 170 m s 2 340 m s 3 520 m s 4 850 m s

5 Four resistances of 15 92 12 92 49 and 10 0 respectively in cyclic order to form Wheatstone s network The resistance that is to be connected in parallel with the resistance of 10 Q to balance the network is JEE Main 2020 22

25 Lenses of power 3D and 5D are combined to form a compound lens An object is placed at a distance of 50 cm from this lens Then the distance of the image from the lens will be 1 25 cm 3 30 cm 2 20 cm 4 40 cm

Test 3 Code A 28 In Wheatstone s network P 49 Q 49 R 49 and S 6 Q The resistance with which S to be shunted in order that the bridge may be balanced is 1 4 2 3 80 P Q ww R ww www S 2 692 4 129

3 Infrared rays 4 Microwaves The de Broglie wavelength of a proton charge 1 6 x 10 19 C mass 1 6 x 10 27 kg accelerated through a potential difference of 1 kV is 1 600 A 3 7 A 2 0 9 x 10 12 m 4 0 9 mm

32 A solenoid of 0 4 m length with 500 turns carries a current of 3 A A coil of 10 turns and of radius 0 01 m carries a current of 0 4 A The torque required to hold the coil with its axis at right angles to that of solenoid in the middle part of it is 1 6x x 10 7N m 2 3 x 10 7N m 4 12 x 10 7 N m 3 9 x 10 7N m

5 A force 57 7 3k N acts on a particle at position i j k m Find torque of this force on the particle about origin 1 47 2 2k N m 2 47 2 2k N m 3 41 2 2k N m 4 107 8 12k N m

When a screw gauge with a least count 0 01 mm is used to measure the diameter of a rod the reading of the sleeve is found to be 1 6 cm and the reading on the thimble is found to be 48 divisions What is the correct diameter of the rod if the zero error for the gauge is 0 003 cm Lo 0

3 In a hydrogen spectrum the shortest wavelength in Balmer Series is The shortest wavelength in Brackett series will be 1 2 3 92 2 4X 4 16 egular

7 The expansion of an ideal gas of mass m at a constant pressure P is given by the straight line B Then the expansion of the same ideal gas of mass 2m at a pressure 2P is given by the straight line Volume B V 1 C 3 B Temperature 2 A 4 Data insufficient

The galvanometer deflection when key K is closed but K is open equal see figure On closing K also and adjusting R to 5 92 the deflection in galvanometer becomes The resistance of the galvanometer is then given by Neglect the internal resistance of battery JEE Main 2019 R R 220 2 www 3 5 2 K K 2 25 92 4 12 2

A spherical shell of radius a carrying a uniform surface charge density o is set spinning with a angular velocity w about a diamter Find the magnetic field at the centre of the shell Also find the equivalent magnetic dipole imoment

Online Mock Test Series for NEET 2020 A current flows in a conductor from east to west The direction of the magnetic field at a point above the conductor is towards 1 East 3 North 2 West 4 South

Estimation of the thermal conductivity of a pure liquid Predict the thermal conductivity of liquid H20 at 40 C and 40 megabars pressure 1 megabar 106 dyn cm2 The isothermal compressibility 1 r dr dp T is 38 X megabar 6 and the density is 0 9938 g cm3 Assume that Cp Cv

3 Two identical magnetic dipoles each of magnetic moment 1 0 A m are placed at a separation of 2 m with their axes perpendicular to each other What is the resultant magnetic field at a point midway between the dipoles a 5x107 T c 2 10 7 T b 5x10 7 T d 10 7 T

mar Y TUF 4 A common emitter circuit has an input resistance of 0 6 ks2 and output resistance of 51 KQ If the current gain is 65 power gain will be 2 3 x 105 1 3 6 105 3 4 x 105 4 4 6 x 105

SolveLancer Test In the given figure ABCD is a parallelogram having area equals to 36 cm and F is midpoint of side AB Area of AAEF is SolveLancer Test E N B D a 18 cm b 4 cm c 20 cm d 9 cm C

C S S e 1 30 3 60 32 In an uniform magnetic field B B a particle of mass m charge q is projected with speed v along y axis from origin Velocity of particle at time 3mm is 2Bq 1 vok 2 45 4 90 Vo 6

View In English A rigid square loop of side length I carrying an electric current is held motionless on a frictionless horizontal tabletop A uniform magnetic field pointing upwards is switched on everywhere the dashed line as shown in the figure and then the loop is released Considering different lengths of the side segments x and y x y which of the following conclusions can you make 1 3 Answer 1 24 If x If x If x If x and y and y l l 2 and y l the loop starts rotating anticlockwise 2 and y l the loop starts rotating anticlockwise 2 27272 the loop starts rotating clockwise more information is required to decide which way the loop starts rotating

Grace is conducting an experiment She starts with 5 samples of lemonade at different temperatures Then she recorded how long it took each sample to freeze solid The graphs shows her results Freezing Time For Lemonade Starting Temperature F 22888 RSRSR 130 120 100 70 40 30 2 3 Time hours What is the average rate of change for the experiment Round to the nearest whole number

A particle is moving along a straight line wit h constant acceleration of 2 metre per sec ond square has a velocity of 6 metre per se cond at t is equal to zero Find the ratio of th e distance and the displacement at t is equa I to 5 second I had seen this sum as an example but the s olution provided was not clear to me Please can you explain the concept to me clearly al ong with the graph

3 55 9 cm 4 20 cm 29 Find the heat current flowing through a hollow thick sphere of inner radius R and other radius 2R Thermal conductivity K Temperature inside is T and outside is T T T 1 2 KR T T 2 41 KR T T 3 8 KR T T 4 10m KR T T 30 Power dissipation through a resistor when an ac source is connected is P If an inductor of

A plane mirror is placed at the bottom of the tank containing a liquid of refractive index n P is a small object at a height h above the mirror An observer O vertically above outside the liquid see P and its image in the mirror The apparent distance between these two will be 1 2 C 2nh n 2h O 0

Six equal positive charges q are placed at the vertices of regular hexagon of side a The charge kept at the centre of the hexagon for the equilibrium of system is a q c 1 83q b q 6 d 1 83q 6 Th If i a b c

he speed s of an accelerating object moving on a strait line is given by the formula s so at where so is the initial speed a is the cceleration and t is the time If the object starts off with a speed of 10 m sec and reaches 16 m sec in 2 minutes what is its acceleration ssume that the acceleration is constant

5 A material B has twice the specific resistance of A A circular wire made of B has twice the diameter of a wire made of A Then for the two wires to have the same resistance the ratio of their respective 1 2 2 1

A simple pendulum consisting of a mass M attached to a string of length L is released from rest at an angle a A pin is located at a distance below the pivot point When the pendulum swings down the string hits the pin as shown in figure The maximum angle which the string makes with the vertical after hitting the pin is Pind L M Pin L 1 0 M

5nT 30 T M 1 29 3 28 In meterbridge experiment when a resistance wire is connected in the left gap the balance point is found at 30 cm When the wire is replaced by another wire the balance point is found at 60 cm Find the balance point when the two wires connected in series 4 3n T 5n T 1 65 9 cm 2 25 cm 3 55 9 cm 4 20 cm Find the heat current flowing through a hollow thick

3 In YDSE the separation between the slits is 2 mm and the separation between slit and screen is 2 m If wavelength of light used is 500 nm and the intensities through the two slits are and 9 then the intensity at a distance mm from centre of screen is 2 10 4 41 1 71 3 16 Two vessels A and Rcontain moles of monoatomic 32

7 Two vessels A and B contain n moles of monoatomic gas at temperature T and n moles of diatomic gas at temperature T respectively Now the two gases are mixed without loss of energy The temperature of the mixture is 1 3 3n T 5n T 3n 50 5n T 3n T m m 2 4 nT n T M 1 3nT 5n T M 1 33

In order to quadruple the resistance of a uniform wire a part of its length was uniformly stretched till the final length of the entire wire was 1 5 times the original length the part of the wire was fraction equal to 1 1 2 3 4 O 1 8 O 1 6 1 10 1 4 0 51