Basic Physics Questions and Answers

dii en W F Fe n 74 A capacitor C 100 F is connected to three resistors each of resistance 1 kn and a battery of emf 9V The switch S has been closed for long time so as to charge the capacitor When switch S is opened the capacitor discharges with time constant C 1kQ wwww 1kQ wwww 1kQ wwww a 33 ms c 100 ms 75 A charged portiola b 5 ms d 50 ms E 6 79

A bulb is placed at depth of 2 7m in water and a floating opaque disc is placed over the bulb so that bulb does not appear visible from the surface The minimum radius of the disc is w 4 3 06m 2 7m 49 m 0 12 m

The dispersive power of material of a lens is 0 04 and mean focal length of lens is 15 cm The difference in focal lengths of lens for violet and rec colour is 3 mm 04 mm O 5 mm 6 mm

Q A rod of length L has non uniform linear mass density given by p x a b where a and b are constants and 0 x L The value of x 2 for the centre of mass of the rod is at JEE Main 2020 a b 2a 3b 3 2a b 2 36 a b L 2 2a 3b 3 L b a b 3 1 2 b L 3a b Adr

779016 A rod of length L is pivoted at one end and is rotated with a uniform angular velocity in a horizontal plane Let T and T2 be the tension at the points L 4 and 3L 4 away from the pivoted ends then A T1 T2 C T T2 atda B T2 T1 D inadequate information

1 A uniform flexible string of length L is stretched between its ends The string is plucked with an amplitude h at a distance 1 3 from one end and then released Investigate the subsequent motion of the string Burd U 1994 Ans y x t sin sin 9h 2 COS nact

Two solutions A and B each of 100 L was made by dissolving 4g of NaOH and 9 8 g of H SO4 in water respectively The pH of the resultant solution obtained from mixing 40 L of solution A and 10 L of solution B is

ed body maintained at T K emits thermal radiation of total energy E with a maximum intensity at frequency v The emissivity of the material is 0 5 If the temperature of the body be increased and maintained at temperature 3T K then i The maximum intensity of the emitted radiation will occur at frequency v 3 ii The maximum intensity of the emitted radiation will occur at frequency 3v iii The total energy of emitted radiation will become 81 E iv The total energy of emitted radiation will become 27 E 1 i ii 3 i iv 2 ii iii 4 i ii iv

index 3 2 The largest value of angle 0 so that ray is totally reflected from face AC when prism immersed in oil of refractive index 5 4 is give by oil O A B sin 3 2 45 O cos 6 oil 0

Two ends of a rod of non uniform area of cross section are maintained at temperature T and T T T as shown in the figure 1 1 X T If I is heat current through the cross section of conductor at distance x from its left face then the variation of I with x is best represented by 3 2 T 4 X

A mgR Assuming that the moon is a sphere of the same mean density as that of the earth and one quarter 99 2 its radius the length of a seconds pendulum on the moon its length on the earth s surface is 99 2 cm s D cm 2 A 24 8 cm B 49 6 cm C 99 2 tationary orbit around a planet at a distance r from the centre of the pl a geostationary

Using the hydrostatic equation what is the pressure in decibars for ocean water with a density of 1027 kg m at 1500 m depth If the water were fresh water what would the pressure be in decibars Use the same depth of 1500 m

A rectangular coil of 10 turns each of area 0 05 m is suspende freely in a uniform magnetic field of induction 0 01 T A current o 30 A is passed through it What is the magnetic moment of the coil What is the maximum torque experienced by the coil

straight line is given by a 41 30 whers a is in m s and is in s The velocity and displacement as function of time is the initia initial velocity is v 3 m s 2 30 3 B v 2 3 C v 2f 30 3 D y f 10r 3

31 A hollow cylinder of specific resistance p inner radius R outer radius 2R and length 1 is as shown in figure What is the net resistance between the inner and outer surfaces a 2R K 3TR P PR b 2 c pln 2 2 pln 2 d 3

1 The length of a metal plate was measured using a vernier calipers of least count 0 01 cm the measurement made were 4 11 cm 4 13 cm 4 21 cm and 4 09 cm Calculate the mean length mean absolute error relative error and percentage error

5 An ideal monoatomic gas at 300 K expands adiabatically to twice its volume The final temperature of gas is a 300 2 b 300 3 300 2 2 3 d 300 2 2 3

Speed of light c 3 x 108 m s The momentum of a proton or a neutron is given as h 1 6 6 10 34 6 6 x 10 kg m s 10 15 The relativistic relation for energy E is given as E p c m c 6 6 10 3 10 0 8176 10 392 04 10 0 6685 x 10 2 392 04 x 10

The LC of screw gauge is 0 01 mm For the reading of diameter of thin wire MSR is 0 5 mm and coinciding CSD is 32 There is negative zero error of 2 divisions hence area of cross section of wire is CO1 O 0 5 mm 2 O 0 0055 cm 2 O 0 55 cm 2 0 05 mm 2

7 Pressure versus temperature graph of an ideal gas is shown in the given figure Density of gas at point A is Po then density of gas at point B will be P a 2po 2P P 2 b Po 3 A B To 3To 3 20 C T muu d 3 po

A block of mass 3 kg with charge of q 30 C is connected to a spring of force constant k 600 N m The block lies on frictionless horizontal track and a uniform electric field E 4 x 106 Vm acts on system as shown The block is released from rest when spring is unstretched The amplitude of oscillation is ooooooo 0 4 m 0 3 m 0 2 m E 9 m 3 kg

M grams of steam at 100 C is mixed with 200 g of ice at its melting point in a thermally insulated container If it produces liquid water at 40 C heat of vaporization of water is 540 cal g and heat of fusion of ice is 80 cal g the value of M is

If alpha particle proton and electron move with the same momentum then their respective de Broglie wavelengths Aa Ap and e are related as Question Type Single Correct Type 1 2 3 a p e a p e a Ap e

Let eo denote the dimensional formula of the permittivity of the vacuum and o that of the permeability of the vacuum If M mass L length T time and I electric current A M L T I B E M L 3T4 1

Q 3 The nrows each containing m cells in series are joined in parallel Maximum current is taken from this combination across an external resistance of 30 resistance If the total number of cells used are 24 and internal resistance of each cell is 0 5 Q ther

The balancing length for a cell is 560 cm in a potentiometer experiment When an external resistance of 10 2 is connected in parallel to the cell the balancing length changes by 60cm If the internal resistance of the cell is 10 is where N is an integer then value of N

X m and 2 Two seperate soap bubbles of radii 3 10 2x 10 m respectively formed of same liquid surface tension 6 5 x 10 2 N m come together to for a double bubble The radius of interface of double bubble is a 6 10 m c 15 x 10 m b 4 10 m 3 d 0 66 10 m

A train is travelling along a horizontal rail at the rate of 90 km hr and rain driven by wind blowing in the direction of motion of train falls at a velocity of 12 5m s making an angle of 30 to the vertical Find the velocity of rain in magnitude and direction as seen from the train 2 4 25 5 5 0 m s inclined at an angle of 30 to the vertical away from train s motion 25 3 2 vertical away from train s motion 25 3 2 m s inclined at an angle of 30 to the 35 3 2 vertical away from train s motion m s inclined at an angle of 60 to the m s inclined at an angle of 60 to the

a 75 b 90 c 105 d 120 D A ray of light is incident on a thick slab of glass of thickness t as shown in the figure The emergent ray is parallel to the incident ray but displaced sideways by a distance d If the angles are small then dis

Two masses m and m m m are connected by a massless flexible and inextensible string passed ove a massless and frictionless pulley The acceleration of the centre of mass is A 71 7 g m1m Correct Answer m1 m m m THY 1280 M M Zero 9 9

Q 38 A volume of 0 5 m of gas at a pressure of 10 bar and 200 C is expanded in a cylinder to 1 2 m at a constant pressure Calculate the amount of work done by the gas and the increase in internal energy Assume cp 1 005 kJ kg K and c 0 712 kJ kg K 900 kJ and 1497 kJ 700 kJ and 1697 kJ 500 kJ and 1797 kJ 200 kJ and 1597 kJ

The pressure at the bottom of a open water tank 3P where Po is atmospheric pressure If water is 2 rd then drawn out till the water level decreases by 3 pressure at the bottom of the tank will be 380 2 1 3 4 Po 3 5P 4 3P0 2 5Po 3

Heat it self does not flow from a body at lower temperature to a body at higher temperature this states 1 law of conservation of momentum 2 First law of thermodynamics 3 law conservation of temperature 4 Second law of thermodynamics

Three balls A B and C are thrown from three points lying on the same horizontal plane as shown in figure 50ms A 1 2 37 3 30ms 4 B 120m Which of the following statement is incorrect 40ms Question Type Single Correct Type 53 C 153 6m None of these Time of flights are same for three balls Three balls meet after 3 second if all the balls are projected simultaneously The balls can never meet if all the balls are projected simultaneously

Refraction of light from air to glass and from air to water are shown in figure i and figure ii below The value of the angle 0 in the case of refraction as shown in figure iii will be i iii Glass Air a 30 60 35 Glass Water b 35 ii 60 Au Water c 60 d 41 13

A person reaches a point directly opposite on the other bank of a flowing river while swimming at a speed of 5 m s at an angle of 120 with the flow The speed of the flow must be A 2 5 m s B 3 m s C 4 m s D 1 5 m s

A plane mirror is placed in y z plane facing towards negative x axis The mirror is moving parallel to y axis with a speed of 2 cm s A point object p is moving in front of the mirror with a velocity 1cm s i 1cm s Then which of the following statements is INCORRECT Question Type Single Correct Type 1 2 3 4 The velocity of image is 1 1 cm s The velocity of image with respect to mirror is cm s The velocity of image with respect to object is 21 cm s The unit vector in the direction 1 of reflected ray is 5

11 A ray incident at a point at an angle of incidence 16 A tank is and is reflected and refracted at the farther surface of 60 enters a glass sphere of refractive index 3 of the sphere The angle between the reflected and apparent tank is m water is m upto the refracted rays at this surface is a 50 b 60 microsco again a 1 00 c 90 d 40 parent depth of a needle lying at the bottom

The shown figure represents a wave front AB which passes from air to another transparent medium and produces a new wave front CD after refraction The refractive index of the medium is PQ is the boundary between air and the medium i fa AB any 4 314 urgent et gola en 34 grad any den med den CD B 90 air D medium

Q 32 Which of the followings are the requirements of an ideal gating syste 1 The molten metal should enter the mould cavity with high velocity 2 It should facilitate complete filling of the mould cavity 3 It should be able to prevent the absorption of air or gases from the surroundings of the molten metal while flowing through it 1 2 and 3 2 and 3 1 and 3

ent measured the diameter of a wire using a screw 1 gauge with least count 0 001 cm and listed the measure ments The correct measurement is 1 5 3 cm 2 5 32 cm 3 5 320 cm 4 5 3200 cm 0 001 cm 44 on lion falleff fel ar an 24 al 2 344 1 5 3 cm 2 5 32 cm 3 5 320 cm 4 5 3200 cm and sell d 5

A small block of mass 4 kg is placed in equilibrium inside a rough bowl which is paraboloid in shape as shown in the figure The height of mass from the ground is 1 8 m The ne contact force by the bowl on the mass has a magnitude g 10 m s 1 8 m 1 20 N 2 40 N 3 80 N

A particle starts from rest and moves with acceleration a 4sin m s where t is in Tct 2 seconds Initially the particle is at origin and moves along x axis then X 1 Maximum speed of the particle is m s 16 TC 2 Direction of acceleration changes alternatively 3 Direction of velocity changes alternatively 8 4 Speed of the particle is T m s at t 1 s

3 Vot bt 4 Vot bt A particle beginning from rest travels a distance S with uniform acceleration and immediately after travels a distance of 38 with uniform velocity followed by a distance 5S with uniform deceleration and comes to rest Then the ratio of a average speed to the maximum speed of the particle is 1 1 5 2 2 5 3 m w 4 4

A screw gauge has some zero error but its value is unknown We have two identical rods When the first rod is inserted in the screw the state of the instrument is shown by diagram 1 When both the rods are inserted together in series then the state is shown by the diagram II What is the zero error of the instrument 1 msd 100 csd 1 mm 12 10

Consider inelastic head on collision between moving neutron and hydrogen atom initially at rest The coefficient of restitution is e 1 2 Assume neutron to be a point mass and hydrogen atom to be a solid sphere After collision the H atom gets excited to higher energy level such that the magnitude of electrostatic potential energy is one eighth of KE of electron in ground state The minimum KE of colliding neutron is 1 17 eV 2 34 eV 4 13 6 eV 3 51 eV

The distance between two rails is 1 2 m The center of gravity of the train is at a height of 2 m from the ground The maximum safe speed of the train on the circular path of radius 150 m is g 9 8 m s 1 21 ms 1 2 42 ms 1 3 63 ms 1

Example 13 7 a When a molecule or an elastic ball hits a massive wall it rebounds with the same speed When a ball hits a massive bat held firmly the same thing happens However when the bat is moving towards the ball the ball rebounds with a different speed Does the ball move faster or slower Ch 6 will refresh your memory on elastic collisions K G b When gas in a cylinder is compressed by pushing in a piston its temperature rises Guess at an explanation of this in terms of kinetic theory using a above c What happens when a compressed gas pushes a piston out and expands What would you observe R d Sachin Tendulkar uses a heavy cricket bat while playing Does it help him in anyway

The diameter of the aperture of a plano convex lens is 6 cm and its maximum thickness is 3 mm If the velocity of light in the material of the lens is 2 x 108 m s its focal length is approximately 1 10 cm 2 15 cm 3 30 cm 4 60 cm

2 4 fastit what will be the magnetic field at the point o 1 Hol 1 4TR I 2 HR 1 R R 0 3 I ww Hol 1 2 R n 1 0 2 TR 4 Hol