# NEET

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

## Biology

Laws of Motion

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Q 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

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Q 2. 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

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Q 3. 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

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Q 4. 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

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Q 5. 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

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Q 6. 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

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Q 7. 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

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Q 8. 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

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Q 9. 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

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Q 10. 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

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Q 11. 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

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Q 12. 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

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Q 13. 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

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Q 14. 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

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Q 15. 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

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Q 16. 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

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Q 17. 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

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Q 18. 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

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Q 19. A cart of mass {tex} \mathrm { M } {/tex} has a block of mass {tex} \mathrm { m } {/tex} attached to it as shown in fig. The coefficient of friction between the block and the cart is {tex} \mu {/tex} . What is the minimum acceleration of the cart so that the block {tex} \mathrm { m } {/tex} does not fall?

A

{tex} \mu g{/tex}

{tex} g / \mu {/tex}

C

{tex} \mu / g {/tex}

D

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

##### Explanation

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Q 20. What is the maximum value of the force {tex} \mathrm { F } {/tex} such that the block shown in the arrangement, does not move?

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

B

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

C

12{tex} \mathrm N {/tex}

D

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

##### Explanation

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Q 21. A block has been placed on an inclined plane with the slope angle {tex} \theta , {/tex} block slides down the plane at constant speed. The coefficient of kinetic friction is equal to

A

{tex} \sin \theta {/tex}

B

{tex} \cos \theta {/tex}

C

g

{tex} \tan \theta {/tex}

##### Explanation

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Q 22. A block of mass {tex} m {/tex} is connected to another block of mass {tex} M {/tex} by a spring (massless) of spring constant {tex} k . {/tex} The blocks are kept on a smooth horizontal plane. Initially the blocks are at rest and the spring is unstretched. Then a constant force {tex} F {/tex} starts acting on the block of mass {tex} M {/tex} to pull it. Find the force of the block of mass {tex} m {/tex} .

A

{tex} \frac { M F } { ( m + M ) } {/tex}

B

{tex} \frac { m F } { M } {/tex}

C

{tex} \frac { ( M + m ) F } { m } {/tex}

{tex} \frac { m F } { ( m + M ) } {/tex}

##### Explanation

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Q 23. A block of mass {tex} m {/tex} is placed on a surface with a vertical cross section given by {tex} y = \frac { x ^ { 3 } } { 6 } {/tex} . If the coefficient of friction is {tex} 0.5 , {/tex} the maximum height above the ground at which the block can be placed without slipping is:

{tex} \frac { 1 } { 6 } \mathrm { m } {/tex}

B

{tex} \frac { 2 } { 3 } \mathrm { m } {/tex}

C

{tex} \frac { 1 } { 3 } \mathrm { m } {/tex}

D

{tex} \frac { 1 } { 2 } \mathrm { m } {/tex}

##### Explanation

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Q 24. Figure shows the speed {tex}V_x{/tex} of a {tex}3.00kg{/tex} mass as a function of time due to two constant forces {tex}\vec{F_1}{/tex} and {tex}\vec{F_2}{/tex} causing the mass to slide on a frictionless surface. Force {tex}F_1=7.00N {/tex} is along the positive x-direction and {tex}F_2=6.00N {/tex} is in the xy-plane. Find the angle between the direction {tex}F_2{/tex} and the positive x axis.

{tex}80.4^{\circ} {/tex}

B

{tex}89.5^{\circ} {/tex}

C

{tex}39.6^{\circ} {/tex}

D

{tex}71.4^{\circ} {/tex}

##### Explanation

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Q 25.

{tex} \frac { 2 \mathrm { ma } } { \mathrm { g } + \mathrm { a } } {/tex}

B

{tex} \frac { 2 \mathrm { ma } } { \mathrm { g } - \mathrm { a } } {/tex}

C

{tex} \frac { \mathrm { ma } } { \mathrm { g } + \mathrm { a } } {/tex}

D

{tex} \frac { \mathrm { ma } } { \mathrm { g } - \mathrm { a } } {/tex}