# JEE Main > Laws of Motion

Explore popular questions from Laws of Motion for JEE Main. This collection covers Laws of Motion previous year JEE Main questions hand picked by popular teachers.

Physics
Chemistry
Maths

Q 1.

Correct4

Incorrect-1

If a body looses half of its velocity on penetrating {tex} 3\mathrm { cm } {/tex} in a wooden block, then how much will it penetrate more before coming to rest?

{tex}1 \mathrm { \ cm } {/tex}

B

{tex} 2\,\mathrm { cm } {/tex}

C

{tex}3\, \mathrm { cm } {/tex}

D

{tex}4\, \mathrm { cm } {/tex}

##### Explanation

Q 2.

Correct4

Incorrect-1

A lift is moving down with acceleration {tex} a {/tex} . A man in the lift drops a ball inside the lift. The acceleration of the ball as observed by the man in the lift and a man standing stationary on the ground are respectively

A

{tex} g , g {/tex}

B

{tex} g - a , g - a {/tex}

{tex} g - a , g {/tex}

D

{tex}a,g{/tex}

##### Explanation

Q 3.

Correct4

Incorrect-1

When forces {tex} F _ { 1 } , F _ { 2 } , F _ { 3 } {/tex} are acting on a particle of mass {tex} m {/tex} such that {tex} F _ { 2 } {/tex} and {tex} F _ { 3 } {/tex} are mutually perpendicular, then the particle remains stationary. If the force {tex} F _ { 1 } {/tex} is now removed then the acceleration of the particle is

{tex} F _ { 1 } / m {/tex}

B

{tex} F _ { 2 } F _ { 3 } / m F _ { 1 } {/tex}

C

{tex} \left( F _ { 2 } - F _ { 3 } \right) / m {/tex}

D

{tex} F _ { 2}/ m {/tex}

##### Explanation

Q 4.

Correct4

Incorrect-1

Two forces are such that the sum of their magnitudes is {tex} \mathrm { 18 N } {/tex} and their resultant is {tex} \mathrm {12 N } {/tex} which is perpendicular to the smaller force. Then the magnitudes of the forces are

A

{tex} 12 \mathrm { N } , 6 \mathrm { N } {/tex}

{tex} 13 \mathrm { N } , 5 \mathrm { N } {/tex}

C

{tex} 10 \mathrm { N } , 8 \mathrm { N } {/tex}

D

{tex} 16 \mathrm { N } , 2 \mathrm { N } {/tex}

##### Explanation

Q 5.

Correct4

Incorrect-1

Speeds of two identical cars are {tex} u {/tex} and 4{tex} u {/tex} at the specific instant. The ratio of the respective distances in which the two cars are stopped from that instant is

A

{tex} 1 : 1 {/tex}

B

{tex} 1 : 4 {/tex}

C

{tex} 1 : 8 {/tex}

{tex} 1 : 16 {/tex}

##### Explanation

Q 6.

Correct4

Incorrect-1

A light string passing over a smooth light pulley connects two blocks of masses {tex} m _ { 1 } {/tex} and {tex} m _ { 2 } {/tex} (vertically). If the acceleration of the system is {tex} g / 8 , {/tex} then the ratio of the masses is

A

{tex} 8 : 1 {/tex}

{tex} 9 : 7 {/tex}

C

{tex} 4 : 3 {/tex}

D

{tex} 5 : 3 {/tex}

##### Explanation

Q 7.

Correct4

Incorrect-1

Three identical blocks of masses {tex} m = 2 \mathrm { kg } {/tex} are drawn by a force {tex} F = 10.2 \mathrm { N } {/tex} with an acceleration of 0.6{tex} \mathrm { ms } ^ { - 2 } {/tex} on a frictionless surface, then what is the tension {tex} ( \mathrm { in \ } \mathrm { N } ) {/tex} in the string between the blocks {tex} B {/tex} and {tex} \mathrm { C } ? {/tex}

A

9.2

3.4

C

4

D

9.8

##### Explanation

Q 8.

Correct4

Incorrect-1

One end of a massless rope, which passes over a massless and frictionless pulley {tex} P {/tex} is tied to a hook {tex} C {/tex} while the other end is free. Maximum tension that the rope can bear is {tex}360N{/tex}. With what value of maximum safe acceleration (in {tex} { ms } ^ { - 2 } ) {/tex} can a man of {tex} 60\mathrm { kg } {/tex} climb on the rope?

A

16

B

6

4

D

8

##### Explanation

Q 9.

Correct4

Incorrect-1

A spring balance is attached to the ceiling of a lift. A man hangs his bag on the spring and the spring reads {tex} \mathrm 49 { N } {/tex} , when the lift is stationary. If the lift moves downward with an acceleration of {tex} 5 \mathrm { m } / \mathrm { s } ^ { 2 } , {/tex} the reading of the spring balance will be

{tex} \mathrm {24 N } {/tex}

B

{tex}74\, \mathrm { N } {/tex}

C

{tex} \mathrm {15 N } {/tex}

D

{tex} \mathrm {49 N } {/tex}

##### Explanation

Q 10.

Correct4

Incorrect-1

Three forces start acting simultaneously on a particle moving with velocity, {tex} \vec { v } {/tex} . These forces are represented in magnitude and direction by the three sides of a triangle {tex} \mathrm { ABC } {/tex} . The particle will now move with velocity

A

less than {tex} \vec { v } {/tex}

B

greater than {tex} \vec { v } {/tex}

C

{tex} | v | {/tex} in the direction of the largest force {tex} B C {/tex}

{tex} \vec { v } , {/tex} remaining unchanged

##### Explanation

Q 11.

Correct4

Incorrect-1

A horizontal force of {tex}10\, \mathrm { N } {/tex} is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is {tex}0.2 {/tex} The weight of the block is

A

{tex}20\, \mathrm { N } {/tex}

B

{tex} \mathrm 50 { N } {/tex}

C

{tex} 100N {/tex}

{tex} \mathrm {2 \ N } {/tex}

##### Explanation

Q 12.

Correct4

Incorrect-1

A marble block of mass {tex}2 \mathrm { kg } {/tex} lying on ice when given a velocity of {tex}6 \mathrm { m } / \mathrm { s } {/tex} is stopped by friction in {tex}10 \mathrm { s } {/tex} . Then the coefficient of friction is

A

0.02

B

0.03

C

0.04{tex} {/tex}

0.06

##### Explanation

Q 13.

Correct4

Incorrect-1

A block of mass {tex} M {/tex} is pulled along a horizontal frictionless surface by a rope of mass {tex} \mathrm { m } {/tex} . If a force {tex} P {/tex} is applied at the free end of the rope, the force exerted by the rope on the block is

A

{tex} \frac { P m } { M + m } {/tex}

B

{tex} \frac { P m } { M - m } {/tex}

C

{tex} P {/tex}

{tex} \frac { P M } { M + m } {/tex}

##### Explanation

Q 14.

Correct4

Incorrect-1

A light spring balance hangs from the hook of the other light spring balance and a block of mass {tex} M {/tex} kg hangs from the former one. Then the true statement about the scale reading is

Both the scales read {tex} M {/tex} kg each

B

The scale of the lower one reads {tex} M {/tex} kg and of the upper one zero

C

The reading of the two scales can be anything but the sum of the reading will be {tex} M \mathrm { \ kg } {/tex}

D

Both the scales read {tex} M / 2 {/tex} kg each

##### Explanation

Q 15.

Correct4

Incorrect-1

A rocket with a lift-off mass {tex} 3.5 \times 10 ^ { 4 } \mathrm { kg } {/tex} is blasted upwards with an initial acceleration of 10{tex} \mathrm { m } / \mathrm { s } ^ { 2 } {/tex} . Then the initial thrust of the blast is

A

{tex} 3.5 \times 10 ^ { 5 } \mathrm { N } {/tex}

{tex} 7.0 \times 10 ^ { 5 } \mathrm { N } {/tex}

C

{tex} 14.0 \times 10 ^ { 5 } \mathrm { N } {/tex}

D

{tex} 1.75 \times 10 ^ { 5 } \mathrm { N } {/tex}

##### Explanation

Q 16.

Correct4

Incorrect-1

Two masses {tex} m _ { 1 } = 5 \mathrm { kg } {/tex} and {tex} m _ { 2 } = 4.8 \mathrm { kg } {/tex} tied to a string are hanging over a light frictionless pulley. What is the acceleration of the masses when left free to move?
{tex} \left( g = 9.8 \mathrm { m } / \mathrm { s } ^ { 2 } \right) {/tex}

A

{tex} 5\,\mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

B

{tex}9.8 \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

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

D

{tex}4.8\, \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

##### Explanation

Q 17.

Correct4

Incorrect-1

A block rests on a rough inclined plame making an angle of {tex} 30 ^ { \circ } {/tex} with the horizontal. The coefficient of static friction between the block and the plane is {tex} 0.8 {/tex}. If the frictional force on the block is {tex} 10\,\mathrm { N } {/tex} , the mass of the block (in {tex} \mathrm { kg } {/tex} ) is
{tex} \left.\text { (take } g = 10 \mathrm { m } / \mathrm { s } ^ { 2 } \right) {/tex}

A

{tex} 1.6 {/tex}

B

{tex} 4.0 {/tex}

{tex}2.0{/tex}

D

{tex}2.5{/tex}

##### Explanation

Q 18.

Correct4

Incorrect-1

A smooth block is released at rest on a {tex} 45 ^ { \circ } {/tex} incline and then slides a distance 'd'. The time taken to slide is 'n' times as much to slide on rough incline than on a smooth incline. The coefficient of friction is

A

{tex} \mu _ { k } = \sqrt { 1 - \frac { 1 } { n ^ { 2 } } } {/tex}

{tex} \mu _ { k } = 1 - \frac { 1 } { n ^ { 2 } } {/tex}

C

{tex} \mu _ { s } = \sqrt { 1 - \frac { 1 } { n ^ { 2 } } } {/tex}

D

{tex} \mu _ { s } = 1 - \frac { 1 } { n ^ { 2 } } {/tex}

##### Explanation

Q 19.

Correct4

Incorrect-1

A parachutist after bailing out falls {tex}50 \mathrm { m } {/tex} without friction. When parachute opens, it decelerates at {tex}2 \mathrm { m } / \mathrm { s } ^ { 2 } {/tex} .He reaches the ground with a speed of {tex}3\, \mathrm{m}/{s}{/tex} . At what height,did he bail out?

A

{tex}182 \mathrm { m } {/tex}

B

{tex}91 \mathrm { m } {/tex}

C

{tex}111 \mathrm { m } {/tex}

{tex}293 \mathrm { m } {/tex}

##### Explanation

Q 20.

Correct4

Incorrect-1

A bullet fired into a fixed target loses half of its velocity after penetrating {tex} 3 \mathrm { cm } . {/tex} How much further it will penetrate before coming to rest assuming that it faces constant resistance to motion?

A

{tex} 2.0 \mathrm { cm } {/tex}

B

{tex}3.0 \mathrm { cm } {/tex}

{tex}1.0 \mathrm { cm } {/tex}

D

{tex}1.5 \mathrm { cm } {/tex}

##### Explanation

Q 21.

Correct4

Incorrect-1

An annular ring with inner and outer radii {tex} R _ { 1 } {/tex} and {tex} R _ { 2 } {/tex} is rolling without slipping with a uniform angular speed. The ratio of the forces experienced by the two particles situated on the inner and outer parts of the ring, {tex} \frac { F _ { 1 } } { F _ { 2 } } {/tex} is

A

{tex} \left( \frac { R _ { \mathrm { I } } } { R _ { 2 } } \right) ^ { 2 } {/tex}

B

{tex} \frac { R _ { 2 } } { R _ { 1 } } {/tex}

{tex} \frac { R _ { 1 } } { R _ { 2 } } {/tex}

D

1

##### Explanation

Q 22.

Correct4

Incorrect-1

The upper half of an inclined plane with inclination {tex} \phi {/tex} is perfectly smooth while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom if the coefficient of friction for the lower half is given by

A

{tex} 2 \cos \phi {/tex}

B

{tex} 2 \sin \phi {/tex}

C

{tex} \tan \phi {/tex}

{tex} 2 \tan \phi {/tex}

##### Explanation

Q 23.

Correct4

Incorrect-1

A particle of mass {tex}0.3 \mathrm { kg } {/tex} subject to a force {tex} F = - k x {/tex} with {tex} k = 15 \mathrm { N } / \mathrm { m } . {/tex} What will be its initial acceleration if it is released from a point {tex} 20\mathrm { cm } {/tex} away from the origin?

A

{tex}15 \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

B

{tex}3 \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

{tex} 10\mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

D

{tex} 5 \mathrm { m } / \mathrm { s } ^ { 2 } {/tex}

##### Explanation

Q 24.

Correct4

Incorrect-1

A block is kept on a frictionless inclined surface with angle of inclination {tex} '\alpha' . {/tex} The incline is given an acceleration {tex} 'a' {/tex} to keep the block stationary. Then {tex} a {/tex} is equal to

A

{tex} g \ \mathrm {cosec} \ \alpha {/tex}

B

{tex}g/\tan\alpha {/tex}

{tex} g \tan \alpha {/tex}

D

g

##### Explanation

Q 25.

Correct4

Incorrect-1

Consider a car moving on a straight road with a speed of {tex}100 \mathrm { m } / \mathrm { s } {/tex} . The distance at which car can be stopped is {tex} \left[ \mu _ { \mathrm { k } } = 0.5 \right] {/tex}

{tex}1000\, m {/tex}

B

{tex}800 m {/tex}

C

{tex}400\, m {/tex}

D

{tex}100\, \mathrm { m } {/tex}