Physics Questions

4 The rate of mass of the gas emitted from rear of a rocket is initially 20 kg s If the speed of the gas relative to the rocket is 800 m s and mass of rocket is 1000 kg then the initial acceleration of the rocket is Take g 10 m s NCERT Pg 110 1 4 m s 2 16 m s 3 6 m s 4 12 m s

A cylinder is placed on a horizontal surface particle is projected with speed u and it crosses the cylinder by just touching at two points as shown in figure Then the initial speed with which the mass projected is vs The value of x is

Q Q Two cylinders P and 2 of equal capacity are connected to each other via a stopcock Cylinder P contains an ideal gas at standard temperature and pressure Cylinder is completely evacuated The entire system is thermally insulated stopcock is suddenly opened What is the effect on internal energy of gas Increases O Decreases No change

Aperture of human eye is 2 mm Assuming the mean wavelength of light be 5000 The angular limit of resolution of eye is nearly 0 1 minute 2 minute O 3 minute O 1 degree

A box of mass 4 kg placed on a horizontal floor is acted upon by a horizontal force F that varies with time t as shown in the given graph If coefficient of static and kinetic frictions are 0 25 then which of the following conclusions can you arrive FIN

7 Two block of masses m and m are connected with the help of a spring of spring constant K initially the spring in its natural length as showsn A sharp impulse is given to mass m so that it acquires a velociy v towards right If the system is kept an smooth floor then find the maximum elongation that the spring will suffer mi k 0000000 m2 Vo

4 3 Example 24 A bird in air is diving vertically over a tank with speed 5 cm s base of tank is silvered A fish in the tank is fing upward along the same line with speed 2 cm s Water level is falling at rate of 2 cm s Take H on Column I cm s A D B C Speed of the image of fish as seen by the bird directly Speed of the image of fish formed after reflection in the mirror as seen by the bird Speed of image of bird relative to the fish looking upwards Speed of image of bird relative to the fish looking downwards in the mirror Column II P 8 Q 6 R 3 S 4 Example 26 Quarter p falls on th a light E whic Ans A Q B R C P D S

A plane surface separates a denser medium of refractive index 1 50 from air A plane wavefront travelling in air is incident on the interface of an angle of incidence 30 The angle of refraction is O sin 0 25 O sin 0 33 O sin 0 9 O sin 0 46

Light of wavelength 500 nm falls on a metal of work function 1 9 eV The stopping potential in this experiment of photo electric effect is O 0 34 V O 0 43 V O 0 58 V O 0 28 V

2 A uniform string of length 20 m is suspended from a rigid support A short wave pulse is introduced at its lowest end It starts moving up the string The time taken to reach the support is Take g 10 ms 1 2n 2s 2 2s 3 2 2s 4 2s

16 In the network shown the potential difference between A and B is R r r r 192 E 3 V E 2 V E3 1V E A R r www E B E 1 1 V 2 2 V 3 3 V 4 4 V wer 8 Pusa Road New Delhi 110005 Ph 011 47623456

A ball A moving with a speed of 99 ms collides directly with another identical ball B moving with a speed v in the opposite direction A comes to rest after the collision If the coefficients of restitution is 0 8 the speed of B lligion is

A double slit apparatus is set up and green light is used to form the interference pattern The green light is then replaced by red light Which of the following changes may allow the spacing of the bright bands on the screen to remain unaffected by the change of light color Given that the distance between the slits is d and that between the plane of the slits and the screen is D Increase D Decreased W Both None

When wave of wavelength 0 2 cm in made to incident normally on a rectangular slit of width 0 004 m then semiangular width of central maxima of diffraction pattern will be 30 O 37 O 45 O 60

5 Two nucleons are at a separation of one fermi Protons have a charge of 16 x 10 19 C The ne nuclear force between them is F if both are neutrons F if both are protons and F3 if one is proton and the other is neutron Then 2005 a F F F3 c F F Fa b F F F3 DE ESE

A circular disc of radius R is removed from a bigger circular disc of radius 2R such that the circumferences of the disc coincide The centre of mass of the new disc from the centre of bigger disc is 1 R 3 R 2 R2 R 3 17

Consider the barometer shown in figure Density of mercury A small hole is made at point S as shown The mercury com out from this hole with speed v equal to ptions 2gh 2gH 2g H h none of these h H S Mercury

The acceleration of a particle moving along straight line decreases linearly from a value of 15 m s2 at t 0 It has zero value at t 5 s At what time the particle acquires its initial speed 1 8 s 2 10 s 4 17 s 3 15 s

If 5 of the energy supplied to a bulb is radiated as visible light how many photons are emitted per second by 100 watt lamp Wavelength c visible light taken is 5 6 x 10 7 m 1 4 1019 1 9 1016 3 4 1020

Case Study 3 The nature position and size of the image formed by a spherical mirror depends on the position of the object in front of it The image formed may be real or virtual for different positions of the object The image is either magnified reduced or has the same size depending on the position of the object Drawing the ray diagrams is an ideal way to illustrate the formation of images by spherical mirrors Each small portion of an extended object of finite size placed in front of a spherical mirror acts like a point source However it is more convenient to consider only two rays for the sake of clarity of the ray diagram These rays are so chosen that it is easy to know their directions after reflection from the mirror The intersection of at least two reflected rays give the position of image of the point object In concave mirror when object is at infinity and rays are coming parallel to principal axis then image is formed

50 Energy of a satellite in circular orbit is Eo The energy required to move the satellite to a circular orbit of 3 times the radius of the initial orbit is Eo 3 d E a Eo 3 b 2E0 GMM

A conductor of area of cross section A having charge carriers each having a charge q is subjected to a potential V The number density of charge carriers in the conductor is n and the charge carriers along with their random motion are moving with average velocity v A current I flows in the conductor If is the current density then O nqV in the direction opposite to charge flow Oj nqv in the direction perpendicular to charge flow Oj nqv in the direction of charge flow O n qV in the direction of charge flow

The minimum and maximum distances of a satellite from the centre of earth are 2R and 4R where R is radius of earth If mass of the earth is M the maximum speed of satellite will be 2 1 3 GM VR 3GM V 2R 4 GM 2R 2GM 3R

39 Half lives of two radioactive nuclei A and B are 10 minutes and 20 minutes respectively If initially a sample has equal number of nuclei then after 60 minutes the ratio of decayed numbers of nuclei A and B will be 1 3 8 2 1 8 3 8 1 A 0 0

2x 5 body of 47 What impulse need to be given to a tunnel passsing through centre of earth at the c released from the surface of earth along a straight of earth to bring it to rest Mass of earth M radius of earth R a m VR b GMm c m d GM V2R VR shells of masses M d Zero R 6

Hypertonic urine formation is a characteristic of kidneys of Fishes and amphibians Amphibians and reptiles Reptiles and birds Birds and mammals Correct Answer nammals Your Answer XX Reptiles and birds

answer out of which ONLY ONE is correct choice questions Each question has 4 choices A B C and D for its 1 If a force F 31 43 5k Newtons is acting on a particle moving on a circle of radius 2m with a speed increasing at the rate of 2ms2 All points on the circle satisfy the equation 3x 4y 5z 0 The power of the force on the particle Increases with time C Is constant B Decreases with time D Zero

In figure block 1 is one fourth the length of block 2 of mass also one fourth No friction exists between block 2 and surface on which it rests Coefficient of friction is u between 1 2 Find the distance block 2 moves when only half of block 1 is still on block 2 Block 1 and block 3 have same masses 2 4m

38 An image of the sun is formed by a lens of focal length 30 cm on the metal surface of a photo electric cell and it produces a current I The lens forming the image is then replaced by another lens of the same diameter but of focal length 15 cm The photoelectric current this case will be In both cases the plate is kept at focal plane and normal to the axis lens 2 21 1 1 2 3 I 4 41

K and K When points A and C are maintained at different temperature no heat flows through the central rod if ons are arranged as shown in the figure They have thermal conductivities K K Ky B 1 K K and K K 3 K K K K Convection A K K K 4 K C D 2 K K K K3 K K K K 2

A particle P is moving in a circle of radius a with uniform speed v C is the centre of the circle and AB is a diameter The angular velocity of P about A and C are in the ratio 1 1 1 2 1 2 3 2 1 4 4 1

A needle of length 10 cm is placed along the principal axis of a concave mirror of focal length 20 cm such that the end closer to mirror is at 40 cm from the mirror The lateral magnification of image formed is wl 3 2 3 43

A satellite is revolving round the earth in an orbit of radius r with time period T If the satellite is revolving round the earth in an orbit of radius Ar Ar r with time period T AT AT T then find 3 AT T 3 Ar 2 r Ar 2 4 2 Ar 3 r 2 Ar

18 An ideal gas expands from state A to B as shown in the figure T P A M B Choose the incorrect option 1 Work done by the gas is positive Work done by the gas continuously increases 3 Work done by the gas is negative 4 TA TB Now Dolbi 410005 Phone 011 47602456

3 28 A conducting wire of resistance 1202 at 20 C is connected in a circuit Due to current flow in it its resistance increases to 24092 Find the final temperature of wire given that temperature coefficient of resistance is 2 x 10 4 C 1 Ans 5020 C

Light with an average flux of 10 w em falls on a non reflecting surface at normal incidence having surface area 40 cm The energy received by the surface during time span of 2 minutes is O 24 kJ O240 J O 12 kJ

WY SECI PHY SECH PHY SEC Question 11 Mul Select Type CHEM SECI CHEM SEC CHEM SECH MATH SEC MATH SECE MATCH QUESTION STATU A dumbbell is constructed by fing small identical bolls at the ends of a light rod of length The dumbbel monds vertically in the corner formed by a frictionless wall and frictionless floor After the bottom end is slighty pushed towards the gre the slide value of which of the following quantities vanish when the upper ball is losing contact with the wall L

Assignment Problem 7 A line charge with linear charge density of p 10 12 C m passes through the center of a sphere If the flux through the surface of the sphere is 1 13x10 3 Vm what is the radius R of the sphere Charged line

14 In the following arrangement table and pulley are smooth Rope is ideal The monkey of mass m moves upward with respect to the rope with acceleration a Find acceleration of block 1 3 M m g a M m 2m g ao M m m 2 4 m g a M m m 2g a M m

A cylinder horizontal is placed on a surface A particle is projected with speed u and it crosses the cylinder by just touching at two points as shown in figure Then the initial speed with which the mass projected is 5x m s The value of x is EO

A toy car is moving on a circular path of radius 10 m on an inclined plane of inclination 30 The coefficient of friction between the tyres and the inclined plane is The maximum constant speed of car such that car does not slip is 5 P ms Assume that width of the car is negligible with respect to radius of circular path Find the value of P g 10m s 3 30

Two balls each of mass 2 kg one at rest undergar oblique collision If collision is perfectly elastic them the angle between their velocities after collision is 1 30 3 45 2 60 4 90

ion ends upon the length of th Assertion In the phenomenon of mutual induction self induction of each of the coil persists Reason Self induction arises due to change in current in the coil itself In mutual induction current changes in both the individual coil

An optical bench has 1 5 m long scale having four equal divisions in each cm While measuring the focal length of a convex lens the lens is kept at 75 cm mark of the scale and the object pin is kept at 45 cm mark The image of the object pin on the other side of the lens overlaps with image pin that is kept at 135 cm mark In this experiment the percentage error in the measurement of the focal length of the lens is 2019

26 A mono atomic gas is filled in a heat insulated horizontal cylindrical is The P container at pressure p and temperature T Density of the gas container is abruptly made to move along its axis with a constant velocity u Find temperature of the gas when a new steady state will establish in the container in gaseous state under a light

A body starts from rest with acceleration 2 m s for some time then retards with 4 m s and finally comes to rest If the total time of journey is 15 sec then what will be maximum velocity 30 m s 40 m s O 15 m s O 20 m s

Two particles having position vectors 61 101 metres and 2 101 6 metres are moving with velocities V 81 61 m s and v 2a 14 m s If they collide after 2 seconds then value of a is 2 4 1 2 3 6 4 8

orbit 5 If an artificial satellite is moving in a circular around the earth with a speed equal to half the height of the satellite above the surface of the earth is magnitude of the escape velocity from the earth the R R a 2 R 2 d 4 f 1 kg infinity to an

2 If linear mass density of a rod of length 3 m lying from y 0 to y 3 m varies as 2 y kg m then position of the centre of mass of the rod from y 0 is nearly at 2 1 7 m 4 2 7 m 1 2 m 3 2 5 m

two 1 7 Two point dipoles pk and k are located at 0 0 0 and 2 1m 0 2m respectively Find the resultant electric field due to the two dipoles at the point 1m 0 0 7 Ans kpk 8