Work, power & energy Questions and Answers

ed cylindrical container is divided into three parts by two insulated pistons which can move without friction The central part of the container contains n moles of oxygen gas The left and right parts of the container have vacuum The natural length of both the spring is 2fp Both the springs are initially compressed by fo Heating of the gas is done with the help of a heating coll H such that pistons move slowly by distance x as shown in the figure Neglect the heat capacity of the container pistons and springs Spring constant of both the spring is k Now answer the following questions 1 30 2 3 The work done by the gas during the given displacement x is A kx C klox B 2klox x x REVIEW BOOKLET 2021 JEEA PART II PHYSIC The change in internal energy of the gas during the given displacement x is A 5kx B 10k x C 5k 2 ox x D can t be calculated 24 The molar heat capacity of the gas during the process is 13 A R lox 4x 3x 2x 2 B 2R MEGACOSM COGNITIONS PRIVATE LATED

A collar B of mass 2kg is constrained to move along a vertical smooth and fixed circular track of radius 5m as shown in figure The spring is in plane of the track and has a spring constant of 200 N m It is underformed when collar is at A It starts from rest at B What is the normal force in N exerted by the track on the collar when it passes through A B 600000000000000 7m D 5m JC

and frequency along the same straight line They Two particles executes SHM of the same amplitude pass one another when going in opposite directions each time their displacement is half their amplitude What is the phase difference between them c 90 d 120 a 60 09 b 30 suspended separately by two spring 6 is

Which of the following happens when the small block of the mass m slides down on a slanted surface m Kinetic energy of the small block changes to potential energy O Potential energy of the small block changes to kinetic energy Potential energy of the small block increases O Kinetic energy of the small block decreases

The chain is released see figure What is the speed when it slips by length TI 2 xxxxx 7 x 3M v BMxgx L x 30g x 34 4x84 1 3 3gL 16 3gL 8 39 4 M L 2 LOY 52 1 34 8 Lt 22 1 5gL 16

A large number of small beads of unit mass each are strung at equal unit distances on a long horizontal wire The beads are initially at rest but can move freely without any friction The bead on the left extreme continuously accelerated towards other beads on the right by applying a constant force of 16 units on it Assuming completely inelastic collisions find the asymptotic speed of the cluster if the collisions are nev ending

One mole of an ideal monatomic gas is t from A to C along the path ABC temperature of the gas at A is To For the pro ABC 2P Po C 8 2V 1 Work done by the gas is RT 2 Change in internal energy of the ga 11R70 2 3 Heat absorbed by the gas is 21RT 2 nr 10

Q2 Find the work done to displace a 5 kg body from 7 2 5 to 4 9 10 under a constant I force F 4i j 3k N containing yoctors 0 3i i k and

20 If g is the acceleration due to gravity on earth s surface the gain in P E of an obje mass m raised from the surface of the earth height equal to the radius R of the earth is 1 mgR 2 2mgR 3 mg 2 4 mg 4

A molecule of a substance has electric dipole moment of magnitude 10 2 C m A mole of this substance is polarised by applying strong electric field of magnitudes 107 Vm1 The direction of field is changed by an angle of 60 The heat released by the substance in aligning its dipole along the new direction of field is 60 J 12 J 15 J 30 J

A small ball of mass 100 g is attached to a light and inextensible string of length 50 cm The string is tied to a support O and the mass m released from point A which is at a horizontal distance of 30 cm from the support Calculate the speed of the ball at its lowest point of the trajectory 30 cm Partick

Water falls from a height of 60 m at the rate of 15 kg e to operate a turbine The losses due to frictional force are 10 of the input energy How much power is generated by the turbine g 10 m s 12 3 kW 7 0 kW 10 2 kW 2 3

1 A ball of mass 0 50 kg is rolling across a table top with a speed of 5 0 m s When the ball reaches the edge of the table it rolls down an incline onto the floor 1 0 meter below without bouncing What is the speed of the ball when it reaches the floor

or the circuit shown in figure 10 50 D 4A D 7A 20 28 V 40 202 40

Two masses m and m at an infinite distance from each other are initially at rest start interacting gravitationally The relative velocity of approach when they are at distance r apart is O O 2G m m r 2G m m r G m m r G m m

Column Il gives certain systems undergoing a process Column I suggests changes in some of the parameters related to the system Match the statements in Column I to the appropriate process es from Column II 2009 Column I A The energy of the system is p increased B Mechanical energy is q provided to the system which is converted into energy of random motion of its parts C Internal energy of the system r is converted in to its mechanical energy D Mass of the system is decreased s t Column II System Process System Process System Process System Process System Process A capacitor initially uncharged It is connected to a battery A gas in an adiabatic container fitted with an adiabatic piston The gas is compressed by pushing the pistion A gas in a rigid container The gas gets cooled due to colder atmosphere surrounding it A heavy nucleus initially at rest The nucleus fissions into two fragments of nearly equal masses and some neutrons are emitted A resistive wire loop The loop is placed in a time varying magnetic field perpendicular to its

The system shown in figure is released from rest with spring at natural length The spring starts extending as soon as it is released if Neglect friction and masses of pulley string and spring A M m B M 2m Eeeeeeee m M m C M m 2 D M m 3

Ideal pulley is pulled by force F upwards If 3 kg moves with constant velocity choose CORRECT statement s A Tension in string is 30 N C Force F is 60 N F 2kg 3kg B Acceleration of 2 kg block is 5 m s D Acceleration of 3 kg block is zero

2 20P After the collision is masses stick each other There is a spring with force constant k between mass B and C no friction between ground and masses a Calculate the speeds v1 and v2 just after the collision b After collusion what will be the maximum compression of the spring Before 20 m A After m B UL mm m

The two same uniform round rigid body are released from rest from the position shown such that it is just able to loop without leaving contact with the track Assuming that radius of the both circular track is same and it is large in comparison to the radius of round body the ratio h h R smooth surface is R Rough surface and no slipping motion 1 must be greater than 1 2 must be less than 1 3 must be equal to 1 4 can be less than or greater than 1 depending

When we neglected air resistance then potential energy is converted into kinetic energy so it is conservative otherwise when we considered air then potential energy is converted into kinetic energy then it is non conservative Both case positive direction of gravity 9 03 PM

Two transparent elevator cars A and B are moving in front of each other Car A is moving up and retarding at a while car B is moving down and retarding at a Person in car A drops a coin inside the car What is the acceleration observed by person in car B B g a a downward A g a downward C g a a downward D None of these

A vertical spring of constant k is kept fixed on a horizontal ground A block of mass 1 kg is kept at the top of the spring and gently released The compression produced in the spring at equilibrium is 2 cm Had the mass been suddenly released the maximum compression in the spring would be 1 1 cm 2 2 cm 3 4 cm 4 8 cm

A bullet of mass m moving vertically upwards instantaneously with a velocity u hits the hanging block of mass m and gets embedded in it as shown in the figure The height through which the block rises after the collision Assume sufficient space above block is wwww R 1 0 m C u 8g D u 4g

A water cooler of storage capacity 120 litres can cool water at a constant rate of P watts In a closed circulation system as shown schematically in the figure the water from the cooler is used to cool an external device that generates constantly 3 kW of heat thermal load The temperature of water fed into the device cannot exceed 30 C and the entire stored 120 litres of water is initially cooled to 10 C The entire system is thermally insulated The minimum value of P in watts for which the device can be operated for 3 hours is Cooler Hot Cold Device Specific heat of water is 4 2 kJ kg 1 K 1 and the density of water is 1000 kg m A 1600 B 2067 C 2533 D 3933

A block of mass m is kept on a rough horizontal surface with coefficient of friction The block is attached with the vertical wall through a spring of spring constant k Spring is compressed by 2 mg k distance and block is released from rest mway ich ch afu quic left c geta gfau gaz 42 zu Ga 1 yech a n Auick TA GEfur Haz f a 2 mg as a ful k Ga am geh c fagh qa 2 mg k A Acceleration of the block just after it is released is ug Teht sich a yech chi d Correct Answer ooooooooo m B Speed of block is maximum when spring attains its natural length ga 34 ya dfs ura gra ac yeh C D Your Answer m Maximum speed of the block is pg k gch xfucd ald Correct Answer m Maximum elongation in the spring is

A block of mass m is suspended by a light thread from an elevator The elevator is accelerating upward with uniform acceleration a The work done by tension on the block during t seconds is m A m g a at B 2 g a at skipped m 2 QUES 6 Correa MY PER SC 1 out

A ball is thrown vertically downwards with velocity 2gh from a height h After colliding with the ground it just reaches the starting point Coefficient of restitution is A 1 2 skipped W B 1 2 6 Correct MY PERI SCC 1

A block of mass m is connected with three spring of spring constant 5K 2K and 3K as shown in figure If the block is slightly displaced then the ratio of displacement of points A and B is A 8 3 C 7 2 5k voooo A B 3 8 D 2 7 2k B 3R E

A rigid body of mass m is moving in a circle of radius r with a constant speed v The force on the body is my and is directed towards the centre What is the work done by this force in moving the body over half the circumference of the circle A B skipped zero 1 01 6 Correct MY PEF

ves on a circular track of ed u The work done by ompletes one circle is NCERT Pg 116 2 Zero m and it rebounds to a age loss of energy is NCERT Pg 125 70 10 c energy twice its body is NCERT Pg 119 2 m s 3 m s ng with velocity of y possessed by it NCERT Pg 119 J 5 J d smooth incline ght h and base mooth horizontal m top of a plane plane the kinetic CERT Pg 121 m h h gs then which equilibrium of a CERT Pg 120 14 The power required by engine of car of m 1000 kg to accelerate it from rest to a spos 72 km h in 20 s is 2 1 kW 1 10 kW 3 100 kW 4 1000 kW 15 A bullet of mass 100 g hits a block of thick 5 cm with a speed of 200 m s It emerge 10 of its initial kinetic energy Then its on INCERT P speed will be 2 20 3 m s 1 20 10 m s 4 10 10 m s 3 20 m s 16 A stone of mass 2 kg tie with the help of the length 2 m and moves in vertical circular The difference between tension in the thread at point and at the highest point is Take g 10 NCERT P 1 60 N 3 30 N 2 120 N 4 240 N 50 m 17 A body is released from position A as show figure The speed of body at position Bis NCERT P 10 m A chain of mass 2 kg is placed th of its length hang 4 B with if the length of chain is 4 mt pulling the hanging portion of surface of the table is 3 2 J If momentum of a body is kinetic energy will be decm 12 4 1 25 3 75 Internal force cannot cha 1 Kinetic energy 2 Total momenturn 3 Total energy of s 4 All of these 1 10 m s 2 10 2 m s 3 20 m s 4 20 2 m s 18 A ball of 4 kg mass moving with velocity 40 m east direction collides with another ball of mass moving with velocity 20 m s in east dired After collision two balls stick together then los kinetic energy is NCERT Pg 1 360 J 2 240 J 3 480 J 4 600 J 19 Which quantity remains conserved in all types d collisions NCERT Pg 129 Y Select correct s equilibrium 1 Potential energ equilibrium 2 Slope of poter is zero at sta 3 A restoring slightly disp position 4 All of these In a conservat function of po corresponding 1 X 3 x 25 If a mass identical r after coll angle of 1 30

Q3 A U tube contains water and methylated spirit separated by mercury The mercury columns in the two arms are at the same level with 10 cm of water in one arm and 12 5 cm of spirit in the other as shown in figure The relative density of the spirit is Water A a 0 6 b 0 8 c 1 0 d 1 25 10 cm 12 5 cm Spirit B Mercury X

3 15 J 4 5 J When a mass of 2 kg is suspended slowly by a spring with its upper end fixed to the ceiling the spring stretches by 1 cm Work done by the spring is g 10 ms 1 0 2 J 2 0 1 J 3 0 4 J 4 None of these

The potential energy of a particle of mass 1 kg in motion along the x axis is given by U 4 1 cos2x J where x is in metres The period of small oscillations in sec is Question Type Single Correct Type 1 2 3 2rt E 2

A block of mass M is connected to a string and rotated with uniform angular speed on a circular track of radius R in the horizontal plane with coefficient of kinetic friction Then choose the correct statement s e is angle between the string and movement of the hand A Work done by the string in one revolution is the negative of work done by friction B Work done by the hand on the string does not depend on angle 0 C Work done by the hand on the string is negative of the work done by friction D Work done by the string on the block is u Ma 2 R

Pls answer without formula And full explain by without using any formula pls A ball is dropped from a height of 10 m hits the ground If coefficient of restitution between the ball and ground is 1 then the percentage loss of energy after the first 2 collision will be 50 25 40

A particle of mass m is attached at one end of a mass less rod and whirled round a verticle circle To complete the circular path the minimum speed given to the particle from lowest position is 1 5g0 3 4gl 0 2 4 2gl gf

MOMENTUM CONSERVATION A particle of mass m is moving with a velocity v another particle of mass my is moving with a velo v Both of them have the same momentum but the different kinetic energies are E and E respective If m m then a E E c E E E Em d E E b

Two objects of the same mass fall from the same height of two smooth fixed inclined plan with different angles When they reach the bottom they should have the same A Kinetic energy B impulse of the normal reaction by the inclined planes C Momentum D The horizontal components of their momentum mi a h 1 T

wheels is g 10 ms 2 K17500 N 2 6500 N 4 1800 N 3 9500 N 16 A ring circular of radius 2 m has mass 100 kg It rolls purely along horizontal flo so that its COM has speed 20 cm s 1 Th work required to stop it is NCERT Pg 179 2 1 2 J 2 3J 43 4 8 J 17 To maintain a rotor at a Upis 1 For three particles of equa at corners of an equilat centre of mass coincides triangle Centre of mass of homo regular shapes consideration lie at 3 When total external fo zero the velocity of 4 For rotation about a noitu voctor lies alg angula

Full se quonia The chain is released see figure What is the speed when it slips by length TA ist L 2 M L 2

Very high table 3 heeeeeee Spring at its natural length Block is released from rest After the above displayed event consider the following two columns List l List II 1 Maximum possible elongation in the P Either zero or 2 g spring II Maximum possible spring force III Maximum acceleration of block A IV Maximum acceleration of block B Q mg k R 2mg k S mg T g U 2 am

The blades of wind mill sweep out a circle of area A 2 m The wind is flowing at velocity v 6 m s 1 perpendicular to circle the density of air is 1 2 kg m 3 What is power generated NCERT Pg 137 Work done by a force is defined as product of in the direction of displacement and magnitude of its displacement 20 at 8 1 160 8 W 2 259 2 W 3 302 5 W 4 239 2 W An electron and a proton are detected cosmic ray experiment The electron ha kinetic energy of 20 keV and proton has Thinking in Context The dimensions of potential energy and unit is INCERT D

questo The chain is released see figure What is the speed when it slips by length 4 3gL V16 L 2 M L 2

1 6 m 3 12 m 25m 4 10 m Raindrop is falling downwards downwards under influence of gravity and opposing resistive force Consider a drop of mass 5 00 g falling from height of 500 m and hits ground with speed of 70 m s 1 What is work done by resistive force NCERT Pg 136 1 7 85 J 2 9 50 J 3 12 75 J 4 13 50 J A cyclist comes to skidding stop in 6 m the force on cycle due 7 which box has bee done during secon 1 175 J 3 75 J A block of mas horizontal surfa enters a rough to x 1 6 m The is inversely pro F X What is final

At a certain point the potential and kinetic energies of a body of mass 4 kg projected vertically up are 200 J 600 J respectively The maximum height reached by the body and the velocity with which it is projected from the ground are O 20 m 20 m s O 20 m 10 m s O 10 m 20 m s O 10 m 10 m s Marks 4 1

What if the amplifiers were connected in parallel What will be the answer then current une base resistance is I KS2 7 10 10 Two amplifiers are connected one after the other in series cascaded The first amplifier has a voltage gain of 10 and the second has a voltage gain of 20 If the input signal is 0 01 volt calculate the output ac signal fabricated from a semiconductor with hand gan

SECTION A A particle of mass m is attached at one end of a mass less rod and whirled round a verticle circle To complete the circular path the minimum speed given to the particle from lowest position is Ov5gr O 2gf OV4gr

A vertical spring with force constant K is fixed on a table A ball of mass m at a height h above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance d The net work done in the process is 1 mg h d Kd 1 2 mg h d Kd 2 3 mg h d 4 mg h d 1 2 Kd 1 Kd jegoncour

Attempt All 35 questions When a mass of 2 kg is suspended slowly by a spring with its upper end fixed to the ceiling the spring stretches by 1 cm Work done by the spring is g 10 ms 2 0 2 J 0 1 J 0 4 J None of these Q MAWOW V