Physics Questions

A container has a hole at a height of 2m If the time taken by the efflux to strike the inclined plane perpendicularly is 1 sec Then the height of liquid level from floor initially is Take g 10 m s Area of tank is very large in comparison with area of hole 2m

Two plane mirrors P and Q are kept at an angle with respect to each other Light falls on P is reflected and then fall on Q and is reflected The emergent ray is opposite to incident ray direction Then the value of 0 is equal to

A block of mass 50 kg resting on a horizontal surface is acted upon by a force F which varies as shown in the figure If the coefficient of friction between the block and surface is 0 2 find the time in second when the block will come to rest g 10 m s F in Newton 200 N 1 2 t in sec

3 Velocity displacement curve of a particle moving in a straight line is as shown Line PB is normal to the curve and line PA is normal to the X axis The instantaneous acceleration of the particle at P is 1 4 A 2 m s AV m s 0 4 O B 1 5 m s A 1 0 B 2 0 C 1m s Sm D zero

Which of the following will change its time period if taken to moon from earth Spring pendulum Torsional pendulum A physical pendulum All of these

8 A prism of refracting angle 60 is made of glass whose refractive indices for red and violet light are respectively 1 514 and 1 530 A white beam of light is incident on the prism which is placed at the minimum deviation position for red light with respect to the incident beam Find i angle of incidence ii the angle Ans i 49 2 ii 50 62 iii 1 42 of emergence of violet light and iii the angular dispersion G Multiple Choice Questions MCQ

Visible light of variable wavelength is incident normally on a thin sheet of plastic film in air The reflected light is a minimum only for 512 nm and in um of the film u 1 28 640 nm in the visible spectrum What is the minimum thickness

A bullet is fired horizontally aiming at an object which starts falling at the instant the bullet is fired Show that the bullet will hit the object

All surfaces are rough What should be the maximum coefficient of friction between block A and the surface under it so that all the blocks move together A 0 25 C 0 20 B 0 5 D the block of mass 4m will never move A mass mass

21 Consider a block sliding over a smooth inclined surface of inclination 0 Relating to Newton s second law applied on the block select the incorrect alternative 1 F 0 3 Fx mg sine Luben 2 F 0 4 Fx 0

08 Cylindrical bucket B with water in it has mass 10 kg balances a mass of 12 kg A on horizontal surface as shown in the figure A place of cork of mass m 2 kg and specific gravity 0 5 is tied to the bottom of the bucket through a light string A is moved horizontally with constant velocity 4 m s as shown Find the ratio of tension T and T at the instant A reaches point C T 1 B 60 A TA 1 m

For the two blocks shown in the adjacent figure an external force of 18 N is applied on the lower block Find the acceleration of the upper block in m s 0 4 0 2 2 kg 4 kg 18N

Two radioactive sources A and B of half lives of 1 hour an 2 hours respectively initially contain the same number of radioactive atoms At the end of two hours their rates of disintegration are in the ratio of to

2 111 A block of mass 10 kg connected to another hollow block of same size and negligible mass by a spring of spring constant 500 N m floats in water as shown in the figure If the compression in the spring is 2 N cm then find the value of N Pwater 1 10 kg m g 10 m s m 10 kg

5 The force acting on a particle F kv k constant If initial velocity of the particle is vo the velocity of particle in terms of time t is 1 v v ekt m vo 3 v v 1 ekt m kt m 2 v v e kt 4 v v 1 e kt m

0 105 The velocity distribution in a viscous flow over a plate is given by u 4y y for y 2m where u velocity in m s at a point distant y from the plate If the coefficient of dynamic viscosity is 1 5 in SI units determine the shear stress at y 0 in N m

0 9 m cross section A is bent to form a circular arc of radius R forming three quarters of a A tube of circle A liquid of density p is flow through the tube with a linear speed v as shown in the figure The net force exerted by the liquid on the tube is A pAv B 1 TAV 4 90 C 2 pav D zero 205

FIGURE 1 35 In a certain region of space electric field is along the z direction throughout The magnitude of electric field is however not constant but increases uniformly along the positive z direction at the rate of 105 NC per metre What are the force and torque experienced by a system having a total dipole moment equal to 107 Cm in the negative z direction

A particle of mass m and charge q enters the region between the two charged plates initially moving along x axis with speed v like particle 1 in Fig 1 33 The length of plate is L and an uniform electric field E is maintained between the plates Show that the vertical deflection of the particle at the far edge of the plate is qEL 2m v2 Compare this motion with motion of a projectile in gravitational field discussed in Secti las cic

A body of mass M is kept on a rough horizontal surface friction coefficient A person is trying to pull the body by applying a horizontal force but the body is not moving The force by the surface on A is F where a F Mg b F Mg 2 d Mg F Mg 1 2 X Mg F Mg V1 u

A small sphere of radius R is held against the inner surface of a larger sphere of radius 6R The masses of large and small spheres are 4M and M respectively This arrangement is placed on a horizontal table as shown There is no friction between any surfaces of contact The small sphere is now released The coordinates of the centre of the large sphere when the smaller sphere reaches the other extreme position is A L 2R 0 JEE 1996 C 2R 0 B L 2R 0 6R M L O R 4M D 2R L 0

Fill in the blanks for Sonometer 1 In sonometer if tension of wire and length of wire becomes double and mass per unit length of wire remain constant then fundamental frequency of wire will becomes of wire and length becomes double and mass of wire remain constant then

Across a metallic conductor of non uniform cross section a constant potential difference is applied The quantity which remains constant along the conductor is a drift velocity c current density b electric field d current

What must be the ratio of the slit width to the wavelength for a single slit to have the first diffraction minimum at 45 0 Ans 1 27

69 A smooth massless wedge is pushed by a horizontal force P P m 0 Ar tr 1 If P 0 than N mgcos0 N Normal reaction received by the block 2 If P 0 than N mgcose 3 If a 0 than N mgcos0 a acceleration of the wedge 4 If P 0 wedge will accelerate towards left

1 The unit of thermal conductivity is a Wm K 1 c Jm K 2015 b JmK d Wm K

A small mass atta to a string rotates on a frictionless table top as shown If the tension in the string is increased by pulling the string causing the radius of the circular motion to decrease by a factor of 2 the kinetic energy of the mass will r 1 Decrease by a factor of 2 2 Remain constant 3 Increase by a factor of 2 4 Increase by a factor of 4

Five point masses m each are kept at five vertices of a regular pentagon Distance of centre of pentagon from any one of the vertices is a Find gravitational potential and field strength at centre In the above problem if any one point mass is removed then what is gravitational potential and magnitude of field strength at centre

A radioactive nucleus decay as follows X X X if the atomic number and the mass number of X are 72 and 180 then the mass number and atomic number of X are 1 172 70 3 172 69 X X orh txo srl 1511A E 2 171 69 4 172 68 I no logo adi

In the system shown in figure tension T2 is xg then what s the value of x g 10 m s T q g 3 700 Ts 1 kg AT2 2 kg AT 3 kg

Two carts of masses 200 kg and 300 kg on horiz are pushed apart Suppose the coefficient of friction between the carts and the rails are same If the 200 kg cart travels a distance of 36 m and stops then the distance travelled by the cart weighing 300 kg is DPMT 2002 a 32 m c 16 m A B b 24 m d 12 m PE 79

The instantaneous angular position of a point o a rotating wheel is given by the equatio 0 t 2t3 6t The torque on the wheel become zero at 1 t 1s 3 t 0 25 s 2 t 0 5 s 4 t 2s

Transverse elastic waves can be propagate in 1 Both solid gas 2 In solid but not gas 3 Neither solid nor gas 4 None

Q 2 A short straight object of length lies along the central axis of a spherical concave mirror at a distance X from the mirror The focal length of the mirror is F If the length of the image in the mirror is then ratio 9 is Assume X and F D w Soup ba straight X rod doja alusy v F gewann allusz t s cov on 7 1 X Boat FJS

A simple pendulum has time period T The point of suspension is now moved upward according to the relation y Kt K 1 m s where y is the vertical displacement The time period now becomes T The ratio of T is g 10 m s T T2 2 1 6 5 2 56 3 1 4 5

2 While walking on ice one should take small steps to avoid slipping This is because smaller steps ensure a larger friction b smaller friction c larger normal force d smaller normal force

Q1 The end Q and R of two thin wires PQ and RS are soldered joined together Initially each of the wires has a length of 1 m at 10 C Now the end P is main tained at 10 C while the end S is heated and main tained at 400 C The system is thermally insulated from its surroundings If the thermal conductivity of wire PQ is twice that of the wire RS and the coefficient of linear thermal expansion of PQ is 1 2 x 10 5 K 1 2016 the change in length of the wire PQ is B 0 90 mm A 0 78 mm C 1 56 mm D 2 34 mm

An electric field line emerges from a positive point charge q at an angle a to the 91 91 Fig 74 FLO straight line connecting it to a negative point charge 92 Fig 74 At what angle will the field line enter the charge 92

Astronomical unit AU is the average distance between the earth and sun approximately 1 5 10 km The speed of light is about 3 0 108 m s The speed of light in astronomical unit per minute is a 0 012 AU min c 1 2 AU min b 0 12 AU min d 12 0 AU min AMU Med

The time period of small oscillation of a uniform rod of length smoothly hinged at one end The rod oscillates in vertical plane

10 A system consists of two identical blocks each of mass m connected by a massless spring of force constant k Initially the system is in equilibrium as shown in the figure The further compression that must be provided to the spring such that the sigo lower block just lifts off the ground is 1 bos ve zolayd 4 16 etnoms 3 yuzimeno nA ansl9 0 ismin eri 1 2 no 3 BIO 14122 Fubunte 10 vo13 1 insin 4mg k mg co bluorie k E orkom vistos vpoloos ouvent SPES hsb ed bluore XSM 1 ine rase joi sbotic en vinc hsd ii 3mg ko snob sid ton leum show riquo v teoria hewanA no lehoism 629 oosqe ent ni eloric oriths w

of the pile on the bottom of the pond Given u of water 4 3 2 A swimming pool of depth D has a plane mirror like bottom It is filled up completely with water u 4 3 A shining object lies at a height H above the surface of water A swimmer floating on the surface of water looks towards the bottom Where shall he see the image of the object Ans as a distance 2D 4H 3 from him in focussed on a point at the bottom of an empty tank Water refractive index

Ex A point source S is placed at distance of 15 cm from a converging lens of focal length 10 cm Where should a i concave mirror ii convex mirror of focal length 12 cm be placed so that real image is formed on object itself 1 1 1 1 V u v i x v 2f 30 2 x 12 54 cm Sol u 15cm f 10cm R 1 15 1 10 v 30 cm ii x v 2f 30 2 x 12 6 cm X V R I

i A mass m is connected by a weightless cable passing over a frictionless pulley to a container of water whose mass is m at t 0 If the container ejects water in downward direction at a constant rate b kg s With a velocity v relative to the container determine the acceleration of m as a function of time 1 L m mo bt g br my mg bt m Figure 4 65

of its image when it is viewed from the direction of B Ans at A 18 Paraxial rays from an infinitely distant object are incident on the surface of a transparent sphere The rays are brought to focus at the vertex of the surface opposite to the point of incidence Find the refractive index of the material of the sphere Ans 2 19 One end of 0 36 m long transparent rod is flat and the other end is spherical having radius 0 10 m

3 a A particle of mass m strikes elastically with a disc of radius R with a velocity v as shown in the figure If the mass of the disc is equal to that of the particle and the surface of the contact is smooth then the velocity of the disc just after the collision is m A 2v 3 B 2 R 2 m o C 3v 2 D v

The moment of inertia of a thin uniform rod of mass M and length L about an axis passing through its midpoint and perpendicular to its length is Io Its moment of inertia about an axis passing through one of its ends and perpendicular to its length is 1 Io ML2 2 2 Io ML2 4 3 Io 2ML2 4 In MI 2

34 The magnetic field at a point P consists of the terrestrial magnetic field and the field produced by current of 9 A flowing through a long straight conductor How should the conductor be placed with spect to P for the resultant magnetic field at this point to be vertical Given BH 0 18 x 10 4 T Ans 10 x 10 2 m east of P with the current flowing upward or 10 x 10 2 m below P with the current flowing from west to east Two more alternate solutions are possible

A man of 50 kg mass is standing in a gravity free space at a height of 10 m above the floor He throws a stone of 0 5 kg mass downwards with a speed 2 m s When the stone reaches the floor the distance of the man above the floor will be 1 20 m 2 9 9 m 3 10 1 m 4 10 m

11 1 1 1963 X 10 23 A battery is connected with a tangent galvanometer and a resistance in series and the deflection of the galvanometer is 60 On placing a resistance in parallel with the galvanometer the deflection is reduced to 30 If the resistance placed in parallel is 1 9th of the galvanometer resistance calculate the ratio of the series resistance and the galvanometer resistance J E E 76 Ans 2 7 notic meridian from its cg by a fine untwisted wire