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.


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}

Explanation