NEET > Work, Energy and Power

Explore popular questions from Work, Energy and Power for NEET. This collection covers Work, Energy and Power previous year NEET questions hand picked by popular teachers.


Q 1.    

Correct4

Incorrect-1

A spring of spring constant {tex}5 \times 10^ {3}{/tex} N/m is stretched initially by 5cm from the unstretched position. Then the work required to stretch it further by another 5cm is

A

12.50{tex} \mathrm { Nm } {/tex}

18.75{tex} \mathrm { Nm } {/tex}

C

25.00{tex} \mathrm { Nm } {/tex}

D

6.25{tex} \mathrm { Nm } {/tex}

Explanation

Q 2.    

Correct4

Incorrect-1

A particle of mass 10 g moves along a circle of radius 6.4{tex} \mathrm { cm } {/tex} with a constant tangential acceleration. What is the magnitude of this acceleration if the kinetic energy of the particle becomes equal to {tex} 8 \times 10 ^ { - 4 } \mathrm { J } {/tex} by the end of the second revolution after the beginning of the motion?

0.1{tex} \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

B

0.15{tex} \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

C

0.18{tex} \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

D

0.2{tex} \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

Explanation

Q 3.    

Correct4

Incorrect-1

A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time {tex} 't' {/tex} is proportional to

A

{tex} t ^ { 3 / 4 } {/tex}

{tex} t ^ { 3 / 2 } {/tex}

C

{tex} t ^ { 1 / 4 } {/tex}

D

{tex} t ^ { 1 / 2 } {/tex}

Explanation

Q 4.    

Correct4

Incorrect-1

A ball is thrown vertically downwards from a height of 20{tex} \mathrm { m } {/tex} with an initial velocity {tex} \mathrm { v } _ { 0 } {/tex}. It collides with the ground and loses 50{tex} \% {/tex} of its energy in collision and rebounds to the same height. The initial velocity {tex} \mathrm { v } _ { 0 } {/tex} is : (Take g = 10 ms{tex}^{- 2}{/tex})

20{tex} \mathrm { ms } ^ { - 1 } {/tex}

B

28{tex} \mathrm { ms } ^ { - 1 } {/tex}

C

10{tex} \mathrm { ms } ^ { - 1 } {/tex}

D

14{tex} \mathrm { ms } ^ { - 1 } {/tex}

Explanation



Q 5.    

Correct4

Incorrect-1

A cord is used to lower vertically a block of mass {tex} \mathrm { M } , {/tex} a distance {tex} \mathrm { d } {/tex} at a constant downward acceleration of {tex} \mathrm { g } / 4 {/tex}. The work done by the cord on the block is

A

{tex} \mathrm { Mg } \frac { \mathrm { d } } { 4 } {/tex}

B

3{tex} \mathrm { Mg } \frac { \mathrm { d } } { 4 } {/tex}

{tex} - 3 \mathrm { Mg } \frac { \mathrm { d } } { 4 } {/tex}

D

{tex} \mathrm { Mg d } {/tex}

Explanation

Q 6.    

Correct4

Incorrect-1

A rubber ball is dropped from a height of 5{tex} \mathrm { m } {/tex} on a plane, where the acceleration due to gravity is not shown. On bouncing it rises to 1.8{tex} \mathrm { m } {/tex} . The ball loses its velocity on bouncing by a factor of

A

{tex} \frac { 16 } { 25 } {/tex}

{tex} \frac { 2 } { 5 } {/tex}

C

{tex} \frac { 3 } { 5 } {/tex}

D

{tex} \frac { 9 } { 25 } {/tex}

Explanation

Q 7.    

Correct4

Incorrect-1

A ball of mass m moving with a constant velocity strikes against a ball of same mass at rest. If e = coefficient of restitution, then what will be the ratio of velocity of two balls after collision?

{tex} \frac { 1 - e } { 1 + e } {/tex}

B

{tex} \frac { e - 1 } { e + 1 } {/tex}

C

{tex} \frac { 1 + e } { 1 - e } {/tex}

D

{tex} \frac { 2 + e } { e - 1 } {/tex}

Explanation

Q 8.    

Correct4

Incorrect-1

A particle of mass {tex} m {/tex} is driven by a machine that delivers a constant power of {tex} k {/tex} watts. If the particle starts from rest the force on the particle at time {tex} t {/tex} is

A

{tex} \sqrt { m k } \ t ^ { - 1 / 2 } {/tex}

B

{tex} \sqrt { 2 m k } \ t ^ { - 1 / 2 } {/tex}

C

{tex} \frac { 1 } { 2 } \sqrt { m k } \ t ^ { - 1 / 2 } {/tex}

{tex} \sqrt { \frac { \mathrm { mk } } { 2 } } \mathrm { t } ^ { - 1 / 2 } {/tex}

Explanation

Q 9.    

Correct4

Incorrect-1

A body of mass 2 kg moving under a force has relation between displacement {tex} x {/tex} and time t as {tex} x = \frac { t ^ { 3 } } { 3 } {/tex} where {tex} x {/tex} is in metre and {tex} t {/tex} is in sec. The work done by the body in first two second will be

A

1.6 joule

16 joule

C

160 joule

D

1600 joule

Explanation

Q 10.    

Correct4

Incorrect-1

A sphere of mass 8{tex} \mathrm { m } {/tex} collides elastically (in one dimension) with a block of mass 2{tex} \mathrm { m } {/tex} . If the initial energy of sphere is {tex} \mathrm { E } {/tex} . What is the final energy of sphere?

A

0.8{tex} \mathrm { E } {/tex}

0.36{tex} \mathrm { E } {/tex}

C

0.08{tex} \mathrm { E } {/tex}

D

0.64{tex} \mathrm { E } {/tex}

Explanation

Q 11.    

Correct4

Incorrect-1

Two similar springs {tex} P {/tex} and {tex} Q {/tex} have spring constants {tex} K _ { p } {/tex} and {tex} K _ { Q } , {/tex} such that {tex} K _ { P } > K _ { Q }{/tex}. They are stretched, first by the same amount (case a,) then by the same force (case b). The work done by the springs {tex} W _ { p } {/tex} and {tex} W _ { Q } {/tex} are related as, in case (a) and case (b), respectively

A

{tex} \mathrm { W } _ { \mathrm { p } } = \mathrm { W } _ { \mathrm { Q } } ; \mathrm { W } _ { \mathrm { p } } = \mathrm { W } _ { \mathrm { Q } } {/tex}

{tex} \mathrm { W } _ { \mathrm { p } } > \mathrm { W } _ { \mathrm { Q } } ; \mathrm { W } _ { \mathrm { Q} } > \mathrm { W } _ { \mathrm { p } } {/tex}

C

{tex} \mathrm { W } _ { \mathrm { p } } < \mathrm { W } _ { \mathrm { Q } } ; \mathrm { W } _ { \mathrm { Q } } < \mathrm { W } _ { \mathrm { p } }{/tex}

D

{tex} \mathrm W_p = \mathrm W_Q ;\mathrm W_p > \mathrm W_Q {/tex}

Explanation

Q 12.    

Correct4

Incorrect-1

In the figure, the variation of potential energy of a particle of mass {tex} \mathrm { m } = 2 \mathrm { kg } {/tex} is represented w.r.t. its {tex} \mathrm { x } {/tex} -coordinate. The particle moves under the effect of this conservative force along the {tex} \mathrm { x } {/tex} -axis.

If the particle is released at the origin then

A

it will move towards positive x-axis

it will move towards negative x-axis

C

it will remain stationary at the origin

D

its subsequent motion cannot be decided due to lack of information

Explanation

Q 13.    

Correct4

Incorrect-1

The potential energy of a certain spring when stretched through distance S is 10 joule. The amount of work done (in joule) that must be done on this spring to stretch it through an additional distance {tex} \mathrm { s } {/tex} , will be

A

20

B

10

30

D

40

Explanation

Q 14.    

Correct4

Incorrect-1

A force applied by an engine of a train of mass {tex} 2.05 \times 10 ^ { 6 } \mathrm { kg } {/tex} changes its velocity from 5 {tex} \mathrm { m } / \mathrm { s } {/tex} to 25 {tex} \mathrm { m } / \mathrm { s } {/tex} in 5 minutes. The power of the engine is

A

1.025{tex} \mathrm { MW } {/tex}

2.05{tex} \mathrm { MW } {/tex}

C

5{tex} \mathrm { MW } {/tex}

D

6{tex} \mathrm { MW } {/tex}

Explanation

Q 15.    

Correct4

Incorrect-1

The relationship between the force {tex} \mathrm { F } {/tex} and position {tex} \mathrm { x } {/tex} of a body is as shown in figure. The work done in displacing the body form {tex} \mathrm { x } = 1 \mathrm { m } {/tex} to {tex} \mathrm { x } = 5 \mathrm { m } {/tex} will {tex} \mathrm { be } {/tex}

A

30{tex} \mathrm { J } {/tex}

15{tex} \mathrm { J } {/tex}

C

25{tex} \mathrm { J } {/tex}

D

20{tex} \mathrm { J } {/tex}

Explanation

Q 16.    

Correct4

Incorrect-1

A body is allowed to fall freely under gravity from a height of 10{tex} \mathrm { m } {/tex} . If it looses 25{tex} \% {/tex} of its energy due to impact with the ground, then the maximum height it rises after one impact is

A

2.5m

B

5.0m

7.5m

D

8.2m

Explanation



Q 17.    

Correct4

Incorrect-1

A block {tex} \mathrm { C } {/tex} of mass {tex} \mathrm { m } {/tex} is moving with velocity {tex} \mathrm { v } _ { 0 } {/tex} and collides elastically with block A of mass {tex} \mathrm { m } {/tex} and connected to another block {tex} \mathrm { B } {/tex} of mass 2{tex} \mathrm { m } {/tex} through spring constant {tex} \mathrm { k }{/tex}. What is {tex} \mathrm { k } {/tex} if {tex} \mathrm { x } _ { 0 } {/tex} is compression of spring when velocity of {tex} \mathrm { A } {/tex} and {tex} \mathrm { B } {/tex} is same?

A

{tex} \frac { \mathrm { mv } _ { 0 } ^ { 2 } } { \mathrm { x } _ { 0 } ^ { 2 } } {/tex}

B

{tex} \frac { \mathrm { mv } _ { 0 } ^ { 2 } } { 2 \mathrm { x } _ { 0 } ^ { 2 } } {/tex}

C

{tex} \frac { 3 } { 2 } \frac { \mathrm { mv } _ { 0 } ^ { 2 } } { \mathrm { x } _ { 0 } ^ { 2 } } {/tex}

{tex} \frac { 2 } { 3 } \frac { \mathrm { mv } _ { 0 } ^ { 2 } } { \mathrm { x } _ { 0 } ^ { 2 } } {/tex}

Explanation

Q 18.    

Correct4

Incorrect-1

Two springs of force constants 300{tex} \mathrm { N } / \mathrm { m } {/tex} (Spring A) and 400{tex} \mathrm { N } / \mathrm { m } {/tex} (Spring B) are joined together in series. The combination is compressed by 8.75 cm. The ratio of energy stored in A and B is {tex} \frac { E _ { A } } { E _ { B } } . {/tex} Then {tex} \frac { E _ { A } } { E _ { B } } {/tex} is equal to:

{tex} \frac { 4 } { 3 } {/tex}

B

{tex} \frac { 16 } { 9 } {/tex}

C

{tex} \frac { 3 } { 4 } {/tex}

D

{tex} \frac { 9 } { 16 } {/tex}

Explanation

Q 19.    

Correct4

Incorrect-1

A body of mass 1 kg begins to move under the action of a time dependent force {tex} \vec F{/tex} = (2t{tex} \hat i{/tex}+3{tex}t^2 \hat j{/tex})N, where {tex} \hat i{/tex}and {tex} \hat j{/tex} are unit vectors along x and y axis. What power will be developed by the force at the time t?

A

{tex} \left( 2 t ^ { 2 } + 3 t ^ { 3 } \right) W {/tex}

B

{tex} \left( 2 t ^ { 2 } + 4 t ^ { 4 } \right) W {/tex}

C

{tex} \left( 2 t ^ { 3 } + 3 t ^ { 4 } \right) W {/tex}

{tex} \left( 2 t ^ { 3 } + 3 t ^ { 5 } \right) W {/tex}

Explanation

Q 20.    

Correct4

Incorrect-1

A bullet of mass 20{tex} \mathrm { g } {/tex} and moving with 600{tex} \mathrm { m } / \mathrm { s } {/tex} collides with a block of mass 4{tex} \mathrm { kg } {/tex} hanging with the string. What is the velocity of bullet when it comes out of block, if block rises to height 0.2{tex} \mathrm { m } {/tex} after collision?

200{tex} \mathrm { m } / \mathrm { s } {/tex}

B

150{tex} \mathrm { m } / \mathrm { s } {/tex}

C

400{tex} \mathrm { m } / \mathrm { s } {/tex}

D

300{tex} \mathrm { m } / \mathrm { s } {/tex}

Explanation



Q 21.    

Correct4

Incorrect-1

A body of mass m kg is ascending on a smooth inclined plane of inclination {tex} \theta \left( \sin \theta = \frac { 1 } { \mathrm { x } } \right) {/tex} with constant acceleration of a m/s{tex}^ { 2 } {/tex} . The final velocity of the body is v m/s. The work done by the body during this motion is (Initial velocity of the body = 0 )

A

{tex} \frac { 1 } { 2 } m v ^ { 2 } ( g + x a ) {/tex}

B

{tex} \frac { m v ^ { 2 } } { 2 } \left( \frac { g } { 2 } + a \right) {/tex}

C

{tex} \frac { 2 m v ^ { 2 } x } { a } ( a + g x ) {/tex}

{tex} \frac { m v ^ { 2 } } { 2 a x } ( g + x a ) {/tex}

Explanation

Q 22.    

Correct4

Incorrect-1

A glass marble dropped from a certain height above the horizontal surface reaches the surface in time {tex} t {/tex} and then continues to bounce up and down. The time in which the marble finally comes to rest is

A

{tex} e ^ { n } t {/tex}

B

{tex} e ^ { 2 } t {/tex}

{tex} t \left[ \frac { 1 + e } { 1 - e } \right] {/tex}

D

{tex} t \left[ \frac { 1 - e } { 1 + e } \right] {/tex}

Explanation



Q 23.    

Correct4

Incorrect-1

The potential energy of a 1 {tex} \mathrm { kg } {/tex} particle free to move along the {tex} \mathrm { x } {/tex} -axis is given by {tex} \mathrm { V } ( \mathrm { x } ) = \left( \frac { \mathrm { x } ^ { 4 } } { 4 } - \frac { \mathrm { x } ^ { 2 } } { 2 } \right) \mathrm { J } {/tex} . The total mechanical energy of the particle is 2{tex} \mathrm { J } {/tex} . Then, the maximum speed (in m/s) is

{tex} \frac { 3 } { \sqrt { 2 } } {/tex}

B

{tex} \sqrt { 2 } {/tex}

C

{tex} \frac { 1 } { \sqrt { 2 } } {/tex}

D

2

Explanation

Q 24.    

Correct4

Incorrect-1

Water falls from a height of 60{tex} \mathrm { m } {/tex} at the rate of 15 kg/s to operate a turbine. The losses due to frictional force are 10{tex} \% {/tex} of energy. How much power is generated by the turbine?( g = 10 m/s{tex}^{ 2 }{/tex})

8.1{tex} \mathrm { kW } {/tex}

B

10.2{tex} \mathrm { kW } {/tex}

C

12.3{tex} \mathrm { kW } {/tex}

D

7.0{tex} \mathrm { kW } {/tex}

Explanation

Q 25.    

Correct4

Incorrect-1

A car of mass {tex} \mathrm { m } {/tex} starts from rest and accelerates so that the instantaneous power delivered to the car has a constant magnitude {tex} \mathrm { P } _ { 0 } {/tex} . The instantaneous velocity of this car is proportional to:

A

{tex} \mathrm { t } ^ { 2 } \mathrm { P } _ { 0 } {/tex}

{tex} t ^ { 1 / 2 } {/tex}

C

{tex} t ^ { - 1 / 2 } {/tex}

D

{tex} \frac { t } { \sqrt { m } } {/tex}

Explanation