NEET > Laws of Motion

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


Q 1.    

Correct4

Incorrect-1

A player stops a football weighing 0.5 kg which comes flying towards him with a velocity of 10{tex} \mathrm { m } / \mathrm { s } {/tex} . If the impact lasts for {tex}1 / 50 {/tex} th sec. and the ball bounces back with a velocity of 15 {tex} \mathrm { m } / \mathrm { s } , {/tex} then the average force involved is

A

250{tex} \mathrm { N } {/tex}

B

1250{tex} \mathrm { N } {/tex}

C

500{tex} \mathrm { N } {/tex}

625{tex} \mathrm { N } {/tex}

Explanation

Q 2.    

Correct4

Incorrect-1

For the given situation as shown in the figure, the value of {tex} \theta {/tex} to keep the system in equilibrium will be

A

{tex} 30 ^ { \circ } {/tex}

{tex} 45 ^ { \circ } {/tex}

C

{tex}0 ^\circ {/tex}

D

{tex} 90 ^ { \circ } {/tex}

Explanation

Q 3.    

Correct4

Incorrect-1

A 5000 kg rocket is set for vertical firing. The exhaust speed is 800{tex} \mathrm { m } / \mathrm { s } {/tex} . To give an initial upward acceleration of 20{tex} \mathrm { m } / \mathrm { s } ^ { 2 } {/tex} , the amount of gas ejected per second to supply the needed thrust will be (Take g = 10 {tex}\mathrm { m } / \mathrm { s } ^ { 2 } {/tex})

A

127.5{tex} \mathrm { kg } / \mathrm { s } {/tex}

B

137.5{tex} \mathrm { kg } / \mathrm { s } {/tex}

C

155.5{tex} \mathrm { kg } / \mathrm { s } {/tex}

187.5{tex} \mathrm { kg } / \mathrm { s } {/tex}

Explanation

Q 4.    

Correct4

Incorrect-1

Which one of the following statements is correct?

A

If there were no friction, work need to be done to move a body up an inclined plane is zero.

If there were no friction, moving vehicles could not be stopped even by locking the brakes.

C

As the angle of inclination is increased, the normal reaction on the body placed on it increases.

D

A duster weighing 0.5{tex} \mathrm { kg } {/tex} is pressed against a vertical board with force of 11{tex} \mathrm { N } {/tex} . If the coefficient of friction is {tex} 0.5 , {/tex} the work done in rubbing it upward through a distance of 10{tex} \mathrm { cm } {/tex} is 0.55{tex} \mathrm { J } {/tex} .

Explanation


Q 5.    

Correct4

Incorrect-1

A stone is dropped from a height {tex} h . {/tex} It hits the ground with a certain momentum {tex} P . {/tex} If the same stone is dropped from a height 100{tex} \% {/tex} more than the previous height, the momentum when it hits the ground will change by:

A

68{tex} \% {/tex}

41{tex} \% {/tex}

C

200{tex} \% {/tex}

D

100{tex} \% {/tex}

Explanation

Q 6.    

Correct4

Incorrect-1

A 3 kg ball strikes a heavy rigid wall with a speed Of 10 m/s at an angle of 60{tex}^\circ{/tex}. It gets reflected with the same speed and angle as shown here. If the ball is in contact with the wall for 0.20s, what is the average force exerted on the ball by the wall?

A

150{tex} \mathrm { N } {/tex}

B

zero

150{tex} \sqrt { 3 } \mathrm { N } {/tex}

D

300{tex} N {/tex}

Explanation

Q 7.    

Correct4

Incorrect-1

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

A

{tex} \mu = \frac { 2 } { \tan \theta } {/tex}

{tex} \mu = 2 \tan \theta {/tex}

C

{tex} \mu = \tan \theta {/tex}

D

{tex} \mu = \frac { 1 } { \tan \theta } {/tex}

Explanation

Q 8.    

Correct4

Incorrect-1

A block of mass {tex} m {/tex} is in contact with the cart {tex} C {/tex} as shown in the figure.

The coefficient of static friction between the block and the cart is {tex} \mu {/tex} . The acceleration {tex} \alpha {/tex} of the cart that will prevent the block from falling satisfies:

A

{tex} \alpha > \frac { m g } { \mu } {/tex}

B

{tex} \alpha > \frac { g } { \mu m } {/tex}

{tex} \alpha \geq \frac { g } { \mu } {/tex}

D

{tex} \alpha < \frac { g } { \mu } {/tex}

Explanation



Q 9.    

Correct4

Incorrect-1

A bridge is in the from of a semi-circle of radius {tex} 40 \mathrm { m } . {/tex} The greatest speed with which a motor cycle can cross the bridge without leaving the ground at the highest point is {tex} \left( \mathrm { g } = 10 \mathrm { m } \mathrm { s } ^ { - 2 } \right) {/tex} (frictional force is negligibly small)

A

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

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

C

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

D

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

Explanation

Q 10.    

Correct4

Incorrect-1

An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, 1 kg first part moving with a velocity of 12{tex} \mathrm { ms } ^ { - 1 } {/tex} and 2{tex} \mathrm { kg } {/tex} second part moving with a velocity of 8{tex} \mathrm { ms } ^ { - 1 } {/tex} . If the third part flies off with a velocity of {tex} 4 \mathrm { ms } ^ { - 1 } , {/tex} its mass would be

5{tex} \mathrm { kg } {/tex}

B

7{tex} \mathrm { kg } {/tex}

C

17{tex} \mathrm { kg } {/tex}

D

3{tex} \mathrm { kg } {/tex}

Explanation

Q 11.    

Correct4

Incorrect-1

A monkey is decending from the branch of a tree with constant acceleration. If the breaking strength is 75{tex} \% {/tex} of the weight of the monkey, the minimum acceleration with which monkey can slide down without breaking the branch is

A

g

B

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

{tex} \frac { \mathcal { g } } { 4 } {/tex}

D

{tex} \frac { \mathcal { g } } { 2 } {/tex}

Explanation

Q 12.    

Correct4

Incorrect-1

A car having a mass of 1000{tex} \mathrm { kg } {/tex} is moving at a speed of 30 metres/sec. Brakes are applied to bring the car to rest. If the frictional force between the tyres and the road surface is 5000 newtons, the car will come to rest in

A

5 seconds

B

10 seconds

C

12 seconds

6 seconds

Explanation

Q 13.    

Correct4

Incorrect-1

A spring is compressed between two toy carts of mass {tex} \mathrm { m } _ { 1 } {/tex} and {tex} \mathrm { m } _ { 2 } {/tex}. When the toy carts are released, the springs exert equal and opposite average forces for the same time on each toy cart. If {tex} v _ { 1 } {/tex} and {tex} v _ { 2 } {/tex} are the velocities of the toy carts and there is no friction between the toy carts and the ground, then:

A

{tex} \mathrm { v } _ { 1 } / \mathrm { v } _ { 2 } = \mathrm { m } _ { 1 } / \mathrm { m } _ { 2 } {/tex}

B

{tex} \mathrm { v } _ { 1 } / \mathrm { v } _ { 2 } = \mathrm { m } _ { 2 } / \mathrm { m } _ { 1 } {/tex}

{tex} \mathrm { v } _ { 1 } / \mathrm { v } _ { 2 }= - \mathrm { m } _ { 2 } / \mathrm { m } _ { 1 }{/tex}

D

{tex} \mathrm { v } _ { 1 } / \mathrm { v } _ { 2 } = - \mathrm { m } _ { 1 } / \mathrm { m } _ { 2 } {/tex}

Explanation

Q 14.    

Correct4

Incorrect-1

A plate of mass {tex} M {/tex} is placed on a horizontal frictionless surface (see figure), and a body of mass {tex} m {/tex} is placed on this plate. The coefficient of dynamic friction between this body and the plate is {tex} \mu {/tex} . If a force 2{tex} \mu {/tex} mg is applied to the body of mass {tex} m {/tex} along the horizontal, the acceleration of the plate will be

{tex} \frac { \mu \mathrm { m } } { \mathrm { M } } \mathrm { g } {/tex}

B

{tex} \frac { \mu m } { ( M + m ) } g {/tex}

C

{tex} \frac { 2 \mu \mathrm { m } } { \mathrm { M } } \mathrm { g } {/tex}

D

{tex} \frac { 2 \mu m } { ( M + m ) } g {/tex}

Explanation

Q 15.    

Correct4

Incorrect-1

The rate of mass of the gas emitted from rear of a rocket is initially 0.1{tex} \mathrm { kg } / \mathrm { sec } {/tex} . If the speed of the gas relative to the rocket is 50{tex} \mathrm { m } / \mathrm { sec } {/tex} and mass of the rocket is 2{tex} \mathrm { kg } {/tex} , then the acceleration of the rocket in {tex} \mathrm { m } / \mathrm { sec } ^ { 2 } {/tex} is

A

5

B

5.2

2.5

D

25

Explanation

Q 16.    

Correct4

Incorrect-1

A plank with a box on it at one end is gradually raised about the other end. As the angle of inclination with the horizontal reaches {tex} 30 ^ { \circ } {/tex} the box starts to slip and slides 4.0{tex} \mathrm { m } {/tex} down the plank in 4.0{tex} \mathrm { s } {/tex} . The coefficients of static and kinetic friction between the box and the plank will be, respectively:

0.6 and 0.5

B

0.5 and 0.6

C

0.4 and 0.3

D

0.6 and 0.6

Explanation

Q 17.    

Correct4

Incorrect-1

Four blocks of same mass connected by cords are pulled by a force {tex} \mathrm { F } {/tex} on a smooth horizontal surface, as shown in fig. The tensions {tex} \mathrm { T } _ { 1 } , \mathrm { T } _ { 2 } {/tex} and {tex} \mathrm { T } _ { 3 } {/tex} will be

A

{tex} T _ { 1 } = \frac { 1 } { 4 } F , T _ { 2 } = \frac { 3 } { 2 } F , T _ { 3 } = \frac { 1 } { 4 } F {/tex}

B

{tex} T _ { 1 } = \frac { 1 } { 4 } F , T _ { 2 } = \frac { 1 } { 2 } F , T _ { 3 } = \frac { 1 } { 2 } F {/tex}

{tex} T _ { 1 } = \frac { 3 } { 4 } F , T _ { 2 } = \frac { 1 } { 2 } F , T _ { 3 } = \frac { 1 } { 4 } F {/tex}

D

{tex} T _ { 1 } = \frac { 3 } { 4 } F , T _ { 2 } = \frac { 1 } { 2 } F , T _ { 3 } = \frac { 1 } { 2 } F {/tex}

Explanation

Q 18.    

Correct4

Incorrect-1

A body of mass {tex} \mathrm { M } {/tex} is kept on a rough horizontal surface {tex} \text { (friction coefficient } \mu ) . {/tex} A person is trying to pull the body by applying a horizontal force but the body is not moving. The force by the surface on the body is {tex} \mathrm { F } , {/tex} then

A

{tex} \mathrm { F } = \mathrm { Mg } {/tex}

B

{tex} \mathrm { F } = \mu \mathrm { Mg } {/tex}

{tex} \mathrm { Mg } \leq \mathrm { F } \leq \mathrm { Mg } \sqrt { 1 + \mu ^ { 2 } } {/tex}

D

{tex} \mathrm { Mg } \geq \mathrm { F } \geq \mathrm { Mg } \sqrt { 1 + \mu ^ { 2 } } {/tex}

Explanation

Q 19.    

Correct4

Incorrect-1

Which one of the following motions on a smooth plane surface does not involve force?

A

Accelerated motion in a straight line

B

Retarded motion in a straight line

Motion with constant momentum along a straight line

D

Motion along a straight line with varying velocity

Explanation

Q 20.    

Correct4

Incorrect-1

A block A of mass {tex} m _ { 1 } {/tex} rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block B of mass {tex} m _ { 2 } {/tex} is suspended. The coefficient of kinetic friction between the block and the table is {tex} \mu _ { k } {/tex} . When the block A is sliding on the table, the tension in the string is

A

{tex} \frac { \left( \mathrm { m } _ { 2 } - \mu _ { \mathrm { k } } \mathrm { m } _ { 1 } \right) \mathrm { g } } { \left( \mathrm { m } _ { 1 } + \mathrm { m } _ { 2 } \right) } {/tex}

{tex} \frac { \mathrm { m } _ { 1 } \mathrm { m } _ { 2 } \left( 1 + \mu _ { \mathrm { k } } \right) \mathrm { g } } { \left( \mathrm { m } _ { 1 } + \mathrm { m } _ { 2 } \right) } {/tex}

C

{tex} \frac { m _ { 1 } m _ { 2 } \left( 1 - \mu _ { k } \right) g } { \left( m _ { 1 } + m _ { 2 } \right) } {/tex}

D

{tex} \frac { \left( \mathrm { m } _ { 2 } + \mu _ { \mathrm { k } } \mathrm { m } _ { 1 } \right) \mathrm { g } } { \left( \mathrm { m } _ { 1 } + \mathrm { m } _ { 2 } \right) } {/tex}

Explanation

Q 21.    

Correct4

Incorrect-1

The upper half of an inclined plane with inclination f 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

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

B

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

C

{tex} \tan \phi {/tex}

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

Explanation

Q 22.    

Correct4

Incorrect-1

A particle describes a horizontal circle in a conical funnel whose inner surface is smooth with speed of 0.5{tex} \mathrm { m } / \mathrm { s } {/tex} . What is the height of the plane of circle from vertex of the funnel?

A

0.25{tex} \mathrm { cm } {/tex}

B

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

C

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

2.5{tex} \mathrm { cm } {/tex}

Explanation

Q 23.    

Correct4

Incorrect-1

You are on a frictionless horizontal plane. How can you get off if no horizontal force is exerted by pushing against the surface?

A

By jumping

By spitting or sneezing

C

By rolling your body on the surface

D

By running on the plane

Explanation

Q 24.    

Correct4

Incorrect-1

The coefficient of static and dynamic friction between a body and the surface are 0.75 and 0.5 respectively. A force is applied to the body to make it just slide with a constant acceleration which is

{tex} \frac { g } { 4 } {/tex}

B

{tex} \frac { g } { 2 } {/tex}

C

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

D

g

Explanation

Q 25.    

Correct4

Incorrect-1

In the system shown in figure, the pulley is smooth and massless, the string has a total mass 5{tex} \mathrm { g } {/tex} , and the two suspended blocks have masses 25{tex} \mathrm { g } {/tex} and 15{tex} \mathrm { g } {/tex} . The system is released from state {tex} \ell = 0 {/tex} and is studied upto stage {tex} \ell ^ { \prime } = 0 {/tex} During the process, the acceleration of block A will be

A

constant at {tex} \frac { \mathrm { g } } { 9 } {/tex}

B

constant at {tex} \frac { \mathrm { g } } { 4 } {/tex}

increasing by factor of 3

D

increasing by factor of 2

Explanation