# 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.

Physics
Chemistry
Biology

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}