Basic Physics Questions and Answers

ht 4 None of these If P 2Q then which of the following is incorrect 1 P n 2 Direc 3 Dime 4 All c it be equal to 2 Q ons of P Q must be same at the ions of P and Q must be same he above

The diagram shows four slabs of different materials with equal thickness placed side by side Heat flows from left to right and the steady state temperature of the interface are given Rank the materials according to their thermal conductivities smallest to the largest d d dd 1 2 3 4 2 1 35 C 30 C 20 C 0 C 15 C 2 1 3 4 3 3 4 1 2 4

20 Two points are at distance r and r from a long string having charge per unit length o The potential difference between the points is proportional to 1 O a o 100 1 2 b log C 4

The refractive index of slab shown in figure varies with distance x from face AB as 1 apparent distance of object observed by observer from face CD will be 1 It A 2t B C D 8t 2 12 3 3 VEL sick to viral 4 None of these The

3 The length of wire when M is hung from it is 1 and is with both M and M hanging The natural length of wire is M 1 1 h 1 M M M 2 M J M M M 4

1 The standard enthalpy of formation of NH3 is 46 0 kJ mol If the enthalpy of 1 formation of H from its atoms is 436 kJ mol and that of N is 712 kJ mol the average bond enthalpy of N H bond in NH3 is a 964 kJ mol 1 c 1056 kJ mol 1 b 352 kJ mol 1 d 1102 kJ mol 1

3 A motor is fixed inside a box which is moving upwards with velocity 5 m s String is winding at the rate 3 m s Then the velocity of block A will be 1 2 5 m s downwards 3 1 m s downwards 5m s DO mos S 2 5 m s downwards 4 2 m s downwards Space for Rough Work

3 11 6 g cc 4 11 7 g cc 28 Two wires A and B of same material have radii in the ratio 2 1 and lengths in the ratio 4 1 The ratio of the normal forces required to produce the same change in the lengths of these two wires is 1 1 1 2 2 1

If a body is moving along a straight path then which of the following is true Distance is always equal to magnitude of displacement O Body is always accelerated O Distance may be greater than the magnitude of displacement O Speed of body will always be zero once in the journey

EXAMPLE 14 Sum and Difference Together Consider vectors A and B having equal magnitude of 5 units and are inclined each other by 60 Find the magnitude of sum and difference of these vectors Sol Given A 5 units B 5 units 0 60 A B and A B B R A B A B B 60 120 A R A B Dot Produ Terms of It is defined as and the magnit direction of fir If then a b a a

3 volume of 1 m at a constant pressure of 100 N m Then it is heated at constant volume by supplying 150 J of energy As a result the internal energy of the gas B D decreases by 50 J increases by 250 J Correct Answer decreases by 250 J increases by 50 J EXPLANATION Isobaric process with Q 0 0 W AU

16 In the arrangement shown in figure block Q is being pulled with constant speed 9 m s in horizontal direction All strings pulleys are ideal then speeds of points A B on string are P A 1 9m s 9m s O 2 9m s 3m s B 9m s Fixed 3 6m s 3m s Vp 9 Vp 2 3 Vp 9 4 9m s 6m s

daughter nuclei respectively in a radioactive decay The Q value of decay is Q and that for decay is Q If me is mass of an electron then which of the following is correct Q Mx My c Q Mx My c M M 2m l

2a sin is silvered on one side as shown in figure x and y are in 37 a cm If a ray incident on surface parallel to x axis and reflected along y axis then the co ordinates of point of incidence are A curved surface given by y 1 2 2 4 TCX Silvered Surface 3a 4 a 3a

A cricket player catches a ball of mass 100 gm moving with velocity of 10 m s If the ball is caught and stopped in 0 02 second the average force exerted by ball on the hand of player is nearly O 51 N 80 N O 25 N 40 N

P Given below are two statements labelled as Assertion A and Reason R Assertion A Current density is defined as current per unit area and is directed along the direction of current Reason R The current density is a scalar quantity Select the most appropriate answer from the options given below a Both A and R are true and R is the correct explanation of A b Both A and R are true but R is not the correct explanation of A c A is true but R is false d A is false and R is also false

A particle is travelling on a curved path In a certain time interval it speed changes from v to however magnitude of change in velocity is 3v then 1 Final velocity is perpendicular to initial velocity 2 Final velocity vector makes an angle of 120 with initial velocity vector 3 Final velocity vector makes an angle of 60 with initial velocity vector 4 None of these

3 15 mm 25 Breaking stress of a wire of radius r is So If radius becomes double then breaking stress of same wire becomes 1 So 3 450 w 2 2So 4 2

lock B of mass m is suspended from a cord of length attached to a cart A of mass M as shown in the figure The horizontal surface on which the cart moves is smooth Initially both the cart and the block are at rest in the position shown Now B is released Take M m 2 kg 0 45 and g 10 m s Answer the following questions 18 19 The acceleration of the cart immediately after the system is released from rest is 1 A 2 m s C m s 10 3 2 C B 5 3 2 10 The tension in the cord immediately after the system is released from rest is A 10 N 10 B 3 m s D 5 m s D N 20 2 3 N

A load of 2 kg produces an extension of 1 mm im a wire of 3 m in length and 1 mm in diameter The Young s modulus of wire will be 1 3 25 1010 Nm 2 2 7 48 x 1012 Nm 3 7 48 x 1010 Nm 4 7 48 x 10 10 Nm 2

The x z plane is the boundary between two transparent medium Medium I with y 0 has refractive index and medium Il with y 0 has refractive index 1 A ray of light in medium l given by e 1 31 is incident on the plane surface of separation If the reflected and refracted rays are perpendicular to each other find the value of 1 3 2 2 3 2 3 33 4 2 srl blen

20 The poten energy function for the force between two atoms in a diatomic molecule is approximately given by a where a and bare b 6 constants and x is the distance between the atoms If the dissociation energy of the molecule is D U x Uat equilibrium 1 D is 6 b U x m 020x12 a c 2a 6 4a d 6 12a 6 6a vid

When frequency of applied alternating voltage is very high then a A capacitor will tend to become SHORT b An inductor will tend to become SHORT c Both A and B d No one will become short

32 Three identical ideal electric dipoles are arranged as shown in the figure The electric field strength at point R is equal to symbols have their usual meaning 1 41 o P 5p 2 R 2 3 P 1 3p 3 4 o

One plate of a capacitor is connected to a spring as shown in figure Area of both the plates is A In steady state separation between the plates is 0 8d spring was unstretched and the distance between the plates was d when the capacitor was uncharged The force constant of the spring is approximately E 000000

14 Two metallic cylinder made of same material and radii r and 2r are joined as shown in figure If top end is fixed and lower end of cylinder B is twisted by angle 8 then angle of twist for cylinder A is both cylinder have same length 1 2 3 4 15 16 0 16 15 17 0 0 160 17

A 3 kg mass is moving in a plane with its x and y coordinates given by x 5t 1 and y 3t 2 Then at t 2 seconds A The net acceleration is 10 26m s B The net acceleration is 37 36m s C The net force acting on 3 kg mass is 112 08 N D The net force acting on 3 kg mass is 146 N

Two blocks of masses m and 2m are placed in contact on a smooth horizontal surface as shown Two forces of magnitudes 10 N and 16 N respectively are applied on system as shown in figure Normal contact force between the blocks is 10 N 16 N 16 N O 14 N O 12 N m 2m

me equipotential surfaces are shown in the region The electric field intensity in the region is given by 20 V 40 V 60 V 80 V Ja fa fa fe 60 60 60 60 30 cm 60 cm 90 cm 200 3 3 200 V m 1 V m 400 3 3 4 100 V m 2 V m

The figure shows the P V plot of an ideal gas taken through a cycle DCBAD then 6Po P 5Po 4Po O O O O L 1 A I I C Vo 2V 3Vo B All of the above I 1 1 maximum temperature will occur during the process C B A negative work is done by the gas in the cycle DCBAD heat flows out of the gas during C B A

Two masses M m and Mm are attached to the ends of a light inextensible str and the string is made to pass over the surface of a smooth fixed pulley When the masses are released from rest Then acceleration and tension in the string A gm M B 2gm M C 2 M m g 2M Mg 2m

A mass of 4 kg lies on a plane making an angle 30 to the horizontal Resolve its weight along and perpendicular to the plane Assume g 10 m s 1 In figure the component of weight along the plane mg sin 30 4 10x 20N The component of weight perpendicular to plane mg cos30 2x10x 3 2 mg sin30 30 Ymg mgcos30

A rocket of initial mass 6000 kg ejects gases at rate of 16 kg sec with constant relative speed of 11 km sec What is the acceleration of rocket 1 minute after the blast 1 25 m s 2 50 m s 3 10 m s 4 35 m s New Lig

A body is thrown vertically upwards a velocity the instants when it goes past a point 100 m from the ground in its upward and downward journey g 9 8 m s 4 28 s A stone is thrown vertically upwards with a velocity of 20 m s When will its speed be 6 m s and at what altitude 1 43 s 2 65 s 18 6 m

Example 12 A wire of length I and cross sectional area A is suspended at one of its ends from a ceiling What will be its strain energy due to its own weight if the density and Young s modulus of the material of the wire be d and Y Solution Consider an elemental length of the wire of length dx at a distance x from the lower end This length is acted upon by the external force equal to the weight of the portion of wire below foron E in x Ada la Cilibriu

A projectile is projected at an a with the horizontal and with a speed of u The angle made by velocity vector with horizontal as a function of time is best related as 1 tan 3 tan usina gt u cos a gt usina gt 2 tan 4 tan usina u cos a gt usina

1 A 3 C 4 D Breaking stress for a material is 2 x 10 N m What maximum length of the wire of this material can so that the wire does not break by own weight Density of material 5 x 10 kg m 1 1 km 2 2 km 3 3 km 4 4 km

method IST India Standard Time is linked to a set of atomic clocks the no of clocks are 1 One 3 Three 2 Two 4 Four

No 17 The magnetic field in a region is given by B Bo the loop is 2 B v d 2a B v d 2a B v d a B v d 2a View In English k A square loop of side d is placed with its edges along the x and y axes The loop is moved with a constant velocity V voi The emf induce y 6 d d

3 In the given graph which of following physica quantities changes their sign Velocity 2V Vo 0 1 Displacement 3 Both 1 and 2 t tim 2 Velocity 4 Acceleration cortically through the

The wires which connect the battery of an automobile to its starting motor carry a current of 300 A for a short time What is the force per unit length between the wires if they are 70 cm long and 1 5 cm apart Is the force attractive or repulsive 2 Points 1 2 N and Attraction 1 2 N and Repulsive 2 4 N and Attractive 2 4 N and Repulsive

13 A highly conducting cylindrical vessel placed on elevated small supports contains an ideal gas under a piston of mass m Area of the base of the cylinder is A The piston is in equilibrium in the mid of the cylinder Friction force between the cylinder and the piston can be ignored Total mass of the cylinder and the gas is M The atmospheric pressure is po Now the piston is slowly pulled upwards find the maximum value of M such that the cylinder can be lifted off the supports PA mg a b c 2p A mg 2g PA mg 2g d It is impossible in this way

Suppose true value of certain length is near 3 3 578 cm student took three reading with different scale a 3 5 cm using 0 1 cm resolution scale b 3 38 cm using 0 01 cm resolution scale c 3 372 cm using 0 001 cm resolution scale then 1 First is more accurate 2 2nd is more accurate 3 3rd is more precise 4 Both 1 and 3 are correct

A ball is thrown from a point at different angles with same speed u and has same range in both cases If h and h are the heights attained in the two cases then h h will be 2u u 2 9 9 b 2g d 4g

Add 6 75 x 10 cm to 4 52 x 10 cm with regard to significant figures 1 7 20 x 10 cm 3 7 20 x 104 cm 2 7 20 x 10 cm 4 720 cm gth of 217 cm and radiu

The centripetal force F acting on a particle 27 moving uniformly in a circle may depend upon mass m velocity v and radius r of the circle Derive the formula for F using the method of dimensions 1 F mv r mr 2 F my r mv

26 Write the dimensions of a in the relation P b x at where P is power x the distance and t the time 1 MOLOTO 2 M LOT2 3 M L T2 4 M LT 1 26

A thin wire has a length of 21 7 cm and radius 0 46 mm Calculate the volume of the wire to correct significant figures 1 0 14 cm 3 0 014 cm 2 0 144 cm 4 0 143 cm

A leaky capacitor Ze 74 5 2 is in series with a coil Z 40 22 and a resistor R 56 2 When a voltage V 200 V is applied I 2 5 A and the p d across R and Z combined is 194 V Find the los in the capacitor Ans 24 3 W

an obtuse angle The graph between terminal velocity along y axis and square of radius along x axis of spherical body of density p allowed to fal through a fluid of density o is a 1 Straight line with positive slope 2 Straight line with negative slope 3 Straight line perpendicular to x axis 4 Straight line perpendicular to y axis