Basic Physics Questions and Answers

34 A given sample of Na2SO4 contains 6 02 x 1022 SO4 ions Calculate i number of Na ions ii number of formula units and iii weight of the sample Ans i 1 204 x 1024 Na ions ii 6 02 x 1022 formula units iii 14 2 g

ose the confect potentiometer arrangement is shown in the figure r A 1 R R 2 X wis J Driving cell has emf and internal resistance r Resistance of potentiometer wire AB is R X is the E cell of emf and internal resistance Balance point J can be obtained for all finite values of 3 B 2 R

The relative density of a metal by hanging a block of the metal from a spring balance and noting that in air the balance read 5 0 05 N while in water it reac 4 0 05 N The relative density would quoted as 1 5 0 05 2 5 11 4 5 6

Consider a parallel plate capacitor having an E inside it as shown in the adjacent figure A particle of mass m and charge q is hanging inside the capacito through a light inextensible string of length The time period of this pendulum for small oscillations is a T 2n b T 2 c T 2n 1 g qE m 8 T 9 E 29gE m d none of these xx 1 q E 2qgE m m

Why will we apply F TL not F T2L As there will be film fo mation and film has 2 layers so we should use 2L but an wer is coming after using L Pls help 13 2 035 10 14 6 Calculate the force required to take away a flat plate of radius 5 cm from the surface of water Given surface tension of water 72 dyne cm Ane 200

1 Gaseous helium filled in a horizontal fixed cylindrical ves separated from its surroundings by a piston of finite mass whic move without friction Inner surface of the vessel as well as of the are coated with a perfectly heat insulating material The ex pressure is increased rapidly to triple of its initial value w changing the ambient temperature How many times of its initial will the volume of helium become when the piston finally stops a b 3 5 3 5 3 5 7 1 3

a 1 0 H coil Ans 159 24 112 16 A coil has an inductance of 1 H At what frequency will it have a reactance of 3140 What capacitance will have the same reactance at that frequency 7 Ans 500 Hz about 1 x 10 F ad to a series

Q10 Two plane mirrors intersect at right angles as shown in figure A light ray incident on first mirror at a point 12 cm from their point of intersection The angle of incidence at first mirror for which the light ray strikes the midpoint Marks 3 0 of second mirror is O A 90 O B 30 O c 45 O D 60 12 00 cm 24 00 cm

The terminal velocity of an object in a viscous fluid is proportional to 1 Sum of densities of both object and fluid 2 Difference of densities of both object and fluid 3 Density of object only 4 Density of viscous fluid only 24

A sports car moves along a straight road with constant acceleration It has an initial velocity y and after traveling a distance of 800 m in 25 s its velocity becomes v 20 m s What is the car s acceleration during this covered distance a b C d e 0 96 m s 1 12 m s 1 28 m s 1 44 m s 1 60 m s 800 m

Answer the following questions

Q14 Reciprocal of bulk modulus is called compressibility If pressure experienced by certain volume of liquid increases by two times the compressibility becomes O A Decreases by half of its original value O 8 Decreases by two times c Compressibility will not vary under pressure D D Increases by two times

A particle is thrown at an angle a sin 3 in air as shown in the figure The angle received from the inside water is water Only one correct answer A 15 B 45 C 30 D 60 43

Two spherical metal balls of the same material with radii 0 2 cm and 0 3 cm are falling through a fluid at constant speeds If the speed of the first ball radius 0 2 cm is 4 cm s What is the speed of the other ball 1 6 cm s 2 8 cm s 3 9 cm s 4 12 cm s

3 When a cation leaves its normal position in the crystal and moves to some interstitial space the defect in the crystal is known as a Schottky defect b F centre c Frenkel defect d non stoichiometric defect

The figure shows an infinite ladder of resistances The resistance in the n th rung of the ladder counted from left is n n 1 ohms A B The effective resistance between the points A and B is A 0 1 B 2 C 2 3 22 622 12 2002 D10

cm B 15 Two vertical conducting cylinders A and B of different cross sections are connected by a thin tube as shown An ideal gas is trapped in the cylinders by two airtight pistons of masses 1 0 kg and 2 0 kg respectively Initially the pistons are at the same height 40 cm above the base of the cylinders If an additional mass of 10 g were gently placed on the piston in the cylinder A which of the following statements correctly describe the new steady state ultimately reached a Pressure of the gas has been increased b Pressure of the gas remains unchanged c Height difference between the pistons becomes 30 cm d Height difference between the pistons becomes 60 cm 16 Two rubber balloons filled with the same ideal gas wh

magnification produced by an astronomical telescope for normal adjustment is 10 and the length of the telescope is 1 1 m The magnification when the image is formed at the least distance of distinct vision is 1 6 2 16 80 The 2 14 1 18

Q6 There is no SI base unit for area because O A We live in a three not a two dimensional world O B Area can be expressed in terms of square meters O c An area has no thickness hence no physical standard can be built O D It is impossible to express square feet in terms of meters

83 In young s double slit experiment 8th maximum of wavelength is at a distance x from its central maximum and 4th maximum of wavelength 22 is at a distance x from its central maximum The ratio X will be

A body is moving through a viscous fluid then choose the incorrect option 1 Viscous force acting on the body depends on density of body 2 Viscous force acting on the body depends on viscosity of fluid 3 Viscous force acting on the body depends on velocity of body 4 Viscous force acting on the body is directed opposite to the direction of l

Q5 A perfect gas in a closed container is maintained at an initial pressure P If all the atoms are replaced by another species of mass half that of the first and their speeds are made double what will be the resultant pressure O A 2 P O B P12 O c Pi D 4 Pipidl

5 Two conducting rods A and B of same length and cross sectional area are connected i In series ii In parallel as shown In both combination a temperature difference of 100 C is maintained If thermal conductivity of A is 3K and that of B is K then the ratio of heat current flowing in parallel combination to that flowing in series combination is A B 100 C 3K 16 i 0 C 3 100 C 1 3K K ii 0 C 1

in example 15 2 can you explain last 4 steps of solution given in ncert h ow sin 80x0 3 3x20 converted tosin 36 12 WAVES VV Fig 15 7 An element of a string at a fixed location oscillates in time with amplitude a and period T as the wave passes over it y 0 t a sin a sin t Now the period of oscillation of the wave is the time it takes for an element to complete one full oscillation That is a sin t asin t T a sin t T Since sine function repeats after every 2 We then relate the wavelength to k through Eq 15 6 2n k 2x 80 0 m 7 85 cm c Now we relate Tto by the relation T 2r a 2n 3 0 s 2 09 s and frequency v 1 T 0 48 Hz The displacement y at x 30 0 cm and time t 20 s is given by y 0 005 m sin 80 0 0 3 3 0 20 0 005 m sin 36 12m 0 005 m sin 1 699 0 005 m sin 97 5 mm 15 4 THE SPEED OF A TRAVELLING WAVE Here again radian could be dropped and the units could be written merely as mr Thus k represents 2 times the number of waves for the total phase difference that can be accommodated per unit length with Sl units m Example 15 2 A wave travelling along a string is described by ux 0 005 sin 80 0 x 3 0 U in which the numerical constants are in Si units 10 005 m 80 0 rad m and 3 0 rad s Calculate tal the amplitude b the wavelength and c the period and frequency of the wave Also calculate the displacement of the wave at a distance x 30 0 cm and time t 20 s Answer On comparing this displacement equation with Eq 15 2 y x t a sin kx ot we find a b the amplitude of the wave is 0 005 m 5 mm the angular wave number k and angular frequency o are k 80 0 m and 3 0 s 2mv 2rk V a distance Ax in time At The speed of the wave is then Ax At We can put the cross on a point with any other phase It will move with the same speed otherwise the wave pattern will not remain fixed The motion of a fixed phase point on the wave is given by kx at constant 15 10 Thus as time t changes the position x of the fixed phase point must change so that the phase remains constant Thus kx wot klx Ax 1 Al or k Ax At 0 Taking Ax At vanishingly small this gives dx dt k Relating to Tand k to A 369 D A Av T En 15 12 a general relation for all 15 12

Q4 a The intrinsic carrier density at room temperature in Ge is 2 37 x 10 9 m if the electron and hole mobilities are 0 38 and 0 18 m V s respectively calculate the resistivity b The intrinsic carrier density is 1 5 10 6 m If the mobility of electron and hole are 0 13 and 0 05 m V s calculate the conductivity

As shown in figure two identical capacitors are connected to a battery of V volts in parallel When capacitors are fully charged their stored energy is U If the key K is opened and a material of dielectric constant E 2 is inserted in each capacitors their stored energy is now U Then r 5 5 U 1 will be V 3 5 HH C 2 K 5 3 C

The position co ordinates of a projectile thrown from ground are given by y 12t 5t2 m and x 5t m The initial speed of throw is Here t is in second 1 10 m s 3 11 m s 2 13 m s 4 17 m s

of mass M is in vertical position and that is able to move up or down without friction as shown in figure If the temperature is increased M 1 Both P and V of the gas will change 2 Only P will increase according to charle s law 3 V will change but not P 4 P will change but not V The pressure of a gas is decided by fan 13 fferent M 1 Pava 2 3 V ufafa 4 Pufafdam 4 1 fo

ns Col A particle of mass 2kg is placed at rest at origin A force F 21 33 5k is acting on particl At t 4sec the position vector of particle is found to be 8i bj 20k Find b 1 12 2 6 3 2 4 10 1 a F 2 3j 5k 2 m P r ut at 1 x y 2k O 0j OK 2 3j 5k 4 2

8 For the phase diagram of water given in figure 8 curves OA AB and AC are respectively P atmospheric pressure B liq solid A vapour T 1 Sublimation curve vaporisation curve and fusion curve 2 Sublimation curve fusion curve and vaporisation curve 3 Fusion curve vaporisation curve and sublimation curve 4 Fusion curve sublimation curve and 3 ACT P1 1 2 3 fay fanfaten A B 4 9 B FE A T

The absolute minimum temperature for an ideal gas 3 therefore inferred by extrapolating the straight line to the axis in the figure given below This temperature is found to be 273 15 and is designated as Pressure 273 15 C 0 C 1 Kelvin temperature 3 Low temperature Gas A Gas B Gas C Temperature 2 Celsius temperature 4 Absolute zero A y 4 fasay any a ZIA TEN GRO ANY S8 FABREGRI TI 273 15 29 273 15 C 0 C 1 TA 31447 3 A B F 2 feu ar 4

From the edge of a vertical cliff 39 2 m high a body is projected vertically upwards with a velocity of 9 8 m s How long does the body take to reach the ground How long does it take to pass through the point of projection With what velocity does it strike the ground 4 s 2 s 29 4 m s

1 The system is released from the rest as shown in the figure All the surfaces are smooth and strings and pulleys are ideal and massless The acceleration of block B just after the release is A m m 2m B

Half life for a radioactive sample is 20 min Find the time interval in between decaying from 33 to 66 occurs 1 40 min ns 3 l T1 2 20 min N N e t N e No 2 60 min In 2 20 min 2 liab INSTITUTE 0 67 et In 0 67 t In In Similarly t t 19 57 min 20 min 100 67 100 34 t t 20 min In 2 100 67 20 min 4 10 min In 2

A body slips from a balloon ascending vertically with a velocity of 24 5 m s The body reache the ground in 20 s What was the height of the balloon at the instant the body slipped from it g 9 8 m s 1470 m

1 Determine the Momem of mertia with respect to the centroidal axes Also find the radius of gyration and polar moment of inertia 15 500 MOM 15 350 650 mm 200

If electron and proton are accelerated by same potential difference 100 V then find the ratio of their de Broglie wavelength M 9 1 x 10 1 kg Mp 1 6825 10 27 kg 1 43 1 ne 12 27 A 0286 2 43 Ne 12 27 Ap 0 286 ela 40 43 4 40 NSTITUTE

85 Both light and sound waves produce diffraction It is more difficult observe diffraction with light waves than sound waves because RO light waves do not require medium wavelength of light waves is far smaller than sound waves 3 light waves are transverse 4 speed of light is far smaller than sound Tec

Two identical metal spheres A B are charged with equal amount If A is charged positively B charged nagatively then 1 Mass of A increase 2 Mass of A decrease 3 Mass of B decrease 4 No off

A block of mass 3m is connected with a string which is wound on pulley of mass m and radius R as shown in the figure If the system is released from rest Then acceleration of the block will be consider pulley as uniform disc x g 5g 3 3m

If electron proton are 1A apart start m towards each other due to mutual attra Estimate acceleration of electron approxim 1 1 4 x 1019 m s2 2 2 5 x 1022 r 3 1 x 10 m s 4 2 3 x 10 8

98 If the collector current changes from 2mA to 3 mA in a transistor when collector emitter voltage is increased from 2V to 10 V the output resistance is 1 1000 2 3 8 x 10 2 2 8000 2 4 500 52

its around the sun with sun at with constant velocity ts around the sun with sun at one d maximum distances of a planet 9 10 4 None of these Force of gravitation between two masses is found to be F in vacuum If both the masses are dipped in water at same distance then new force will be 1 F 3 F 2 F 4 Cannot say Two point masses mand Am are separated by a

Paragraph for questions 24 27 A block of mass 15 kg is placed over a frictionless horizontal surface as shown in Fig 4 120 Another block of mass 10 kg is placed over it that is connected with a light string passing over tow pulleys fastened to the 15 kg block A force F 80 N is applied horizontally to the free end of the string Friction coefficient between two blocks is 0 6 The portion of the string between 10 kg block and upper pulley is horizontal Pulley string and connecting rods are massless take g 10 m s fam Smooth 10 kg 0 6 15 kg Figure 4 120 O F 80 N

If a EM wave traveling in vacuum in y direction has magnetic field B 8 10 k Then value of electric field E is 1 24 1 2 eliable INSTITUTE 2 24 i 3 2 6x10 16 1 4 2 6 10 6 1 Address Reliable Institute A 10 Road No 1 IPIA Kota 324005 Rajasthan INDIA visit us at www reliablekota com Email info reliablekota com Call us 91 744 2665544 11

Two trains 200 m and 150 m long are running on parallel rails at the rate of 40 kmph and 45 kmph respectively If they are running in the same direction What distance the longer train moves during crossing

48 Read following statements carefully and mark the correct option Statement 1 With the displacement wave we can produce a pressure wave and Statement 2 Displacement and pressure wave both are having the phase difference T 2 1 Statement 1 is True Statement 2 is True Statement 2 is a correct explanation for Statement 1 2 Statement 1 is True Statement 2 is True Statement 2 is not a correct explanation for Statement 1 3 Statement 1 is True Statement 2 is False 4 Statement 1 is False Statement 2 is True

6 Calculate final velocity of the particle of mass 2kg if initial velocity of it is 6 m s A force if it is acted on it and whose variation with time has been shown below F N 10 m s 6 m s 12 m s t sec

xample 18 Three particles of masses m 2m and 3m are placed at the comers of an equilateral triangle of side a Calculate 0 0 The potential energy of the system The work done on the system if the side of the triangle is changed from a to 2a Assume the potential energy to be zem when the separation is infinity

34 A series LCR circuit is connected to an ac source of variable frequency When the frequency is increased continuously starting from very small value the power factor 1 Goes on increasing continuously 2 Goes on decreasing continuously Remains constant Q s R Z