NEET > Gravitation

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


Q 1.    

Correct4

Incorrect-1

The radius of a planet is {tex} 1/ 4 ^ { \text {th } } {/tex} of {tex} R _ { e } {/tex} and its acc. due to gravity is 2 g. What would be the value of escape velocity on the planet, if escape velocity on earth is {tex} v _ { e } {/tex}.

{tex} \frac { \mathrm { v } _ { \mathrm { e } } } { \sqrt { 2 } } {/tex}

B

{tex} \mathrm { v } _ { \mathrm { e } } \sqrt { 2 } {/tex}

C

2{tex} \mathrm { v } _ { \mathrm { e } } {/tex}

D

{tex} \frac { \mathrm { V } _ { \mathrm { e } } } { 2 } {/tex}

Explanation

Q 2.    

Correct4

Incorrect-1

A projectile is fired vertically from the Earth with a velocity {tex} \mathrm { kv } _ { \mathrm { e } } {/tex} where {tex} \mathrm { v } _ { \mathrm { e } } {/tex} is the escape velocity and {tex} \mathrm { k } {/tex} is a constant less
than unity. The maximum height to which projectile rises, as measured from the centre of Earth, is

A

{tex} \frac { R } { k } {/tex}

B

{tex} \frac { R } { k - 1 } {/tex}

{tex} \frac { R } { 1 - k ^ { 2 } } {/tex}

D

{tex} \frac { R } { 1 + k ^ { 2 } } {/tex}

Explanation

Q 3.    

Correct4

Incorrect-1

A solid sphere of uniform density and radius R applies a gravitational force of attraction equal to {tex} \mathrm { F } _ { 1 } {/tex} on a particle placed at A, distance {tex}2 \mathrm { R } {/tex} from the centre of the sphere.

A spherical cavity of radius {tex} \mathrm { R } / 2 {/tex} is now made in the sphere as shown in the figure. The sphere with cavity now applies a gravitational force {tex} \mathrm { F } _ { 2 } {/tex} on the same particle placed at {tex} \mathrm { A } {/tex} . The ratio {tex} \mathrm { F } _ { 2 } / \mathrm { F } _ { 1 } {/tex} will be

A

{tex}1 / 2 {/tex}

B

3

C

7

{tex}1 / 9 {/tex}

Explanation



Q 4.    

Correct4

Incorrect-1

A geostationary satellite is orbiting the earth at a height of 5{tex} \mathrm { R } {/tex} above that surface of the earth, R being the radius of the
earth. The time period of another satellite in hours at a height of 2{tex} \mathrm { R } {/tex} from the surface of the earth is :

A

5

B

10

6{tex} \sqrt { 2 } {/tex}

D

{tex} \frac { 6 } { \sqrt { 2 } } {/tex}

Explanation



Q 5.    

Correct4

Incorrect-1

A satellite of mass {tex} m {/tex} is orbiting around the earth in a circular orbit with a velocity {tex} \mathrm { v } {/tex} . What will be its total energy?

A

{tex} ( 3 / 4 ) \mathrm { mv } ^ { 2 } {/tex}

B

{tex} ( 1 / 2 ) \mathrm { mv } ^ { 2 } {/tex}

C

{tex} \mathrm { mv } ^ { 2 } {/tex}

{tex} - ( 1 / 2 ) m v ^ { 2 } {/tex}

Explanation

Q 6.    

Correct4

Incorrect-1

The gravitational force of attraction between a uniform sphere of mass {tex} \mathrm { M } {/tex} and a uniform rod of length {tex} l {/tex} and mass {tex} \mathrm { m } {/tex} oriented as shown is

{tex} \frac { \mathrm { GMm } } { \mathrm { r } ( \mathrm { r } + l ) } {/tex}

B

{tex} \frac { \mathrm { GM } } { \mathrm { r } ^ { 2 } } {/tex}

C

{tex} \mathrm { Mmr } ^ { 2 } + l {/tex}

D

{tex} \left( \mathrm { r } ^ { 2 } + I \right) \mathrm { mM } {/tex}

Explanation





Q 7.    

Correct4

Incorrect-1

If the gravitational force between two objects were proportional to 1{tex} / \mathrm { R } \left( \text { and not as } 1 / \mathrm { R } ^ { 2 } \right) {/tex} where {tex} \mathrm { R } {/tex} is separation
between them, then a particle in circular orbit under such a force would have its orbital speed v proportional to

A

{tex} 1/ R ^ { 2 } {/tex}

{tex} \mathrm { R } ^ { 0 } {/tex}

C

{tex} \mathrm { R } ^ { 1 } {/tex}

D

{tex}1 / \mathrm { R } {/tex}

Explanation

Q 8.    

Correct4

Incorrect-1

A satellite of mass {tex} m {/tex} revolves around the earth of radius {tex} R {/tex} at a height 'x' from its surface. If {tex} g {/tex} is the acceleration due to
gravity on the surface of the earth, the orbital speed of the satellite is

A

{tex} \frac { \mathrm { g } \mathrm { R } ^ { 2 } } { \mathrm { R } + \mathrm { x } } {/tex}

B

{tex} \frac { \mathrm { gR } } { \mathrm { R } - \mathrm { x } } {/tex}

C

{tex} \mathrm { g } \mathrm { x } {/tex}

{tex} \left( \frac { \mathrm { gR } ^ { 2 } } { \mathrm { R } + \mathrm { x } } \right) ^ { 1 / 2 } {/tex}

Explanation



Q 9.    

Correct4

Incorrect-1

A body is projected up with a velocity equal to {tex} 3/ 4 {/tex} th of the escape velocity from the surface of the earth. The height it reaches from the centre of the earth is (Radius of the earth = R)

A

{tex} \frac { 10 \mathrm { R } } { 9 } {/tex}

{tex} \frac { 16 R } { 7 } {/tex}

C

{tex} \frac { 9 \mathrm { R } } { 8 } {/tex}

D

{tex} \frac { 10 \mathrm { R } } { 3 } {/tex}

Explanation



Q 10.    

Correct4

Incorrect-1

A Planet is revolving around the sun.

Which of the following is correct option?

The time taken in travelling DAB is less than that for BCD

B

The time taken in travelling DAB is greater than that for BCD

C

The time taken in travelling CDA is less than that for ABC

D

The time taken in travelling CDA is greater than that for ABC

Explanation

Q 11.    

Correct4

Incorrect-1

The acceleration due to gravity on the planet {tex} A {/tex} is 9 times the acceleration due to gravity on planet {tex} B {/tex} . A man jumps to
a height of 2{tex} \mathrm { m } {/tex} on the surface of {tex} \mathrm { A } {/tex} . What is the height of jump by the same person on the planet {tex} \mathrm { B } {/tex} ?

A

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

B

{tex} \frac { 2 } { 9 } \mathrm { m } {/tex}

18{tex} \mathrm { m } {/tex}

D

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

Explanation



Q 12.    

Correct4

Incorrect-1

If suddenly the gravitational force of attraction between the earth and a satellite revolving around it becomes zero, then the satellite will

A

continue to move in its orbit with same speed

move tangentially to the original orbit with same speed

C

become stationary in its orbit

D

move towards the earth

Explanation

Q 13.    

Correct4

Incorrect-1

Mass {tex} \mathrm { M } {/tex} is divided into two parts {tex} \mathrm { xM } {/tex} and {tex} ( 1 - \mathrm { x } ) \mathrm { M } {/tex} . For a given separation, the value of {tex} \mathrm { x } {/tex} for which the gravitational attraction between the two pieces becomes maximum is

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

B

{tex} \frac { 3 } { 5 } {/tex}

C

1

D

2

Explanation

Q 14.    

Correct4

Incorrect-1

The potential energy of a satellite, having mass {tex} \mathrm { m } {/tex} and rotating at a height of {tex} 6.4 \times 10 ^ { 6 } \mathrm { m } {/tex} from the earth surface, is

A

{tex} - \mathrm { mgR } _ { \mathrm { e } } {/tex}

B

{tex} - 0.67 \mathrm { mgR_{e} } {/tex}

{tex} - 0.5 \mathrm { mgR } _ { \mathrm { e } } {/tex}

D

{tex} - 0.33 \mathrm { mgR } _ { \mathrm { e } } {/tex}

Explanation



Q 15.    

Correct4

Incorrect-1

If the radius of the earth were to shrink by {tex} 1 \% , {/tex} with its mass remaining the same, the acceleration due to gravity on the earth's surface would

A

decrease by 1{tex} \% {/tex}

B

decrease by 2{tex} \% {/tex}

C

increase by 1{tex} \% {/tex}

increase by 2{tex} \% {/tex}

Explanation



Q 16.    

Correct4

Incorrect-1

Suppose the law of gravitational attraction suddenly changes and becomes an inverse cube law i.e. {tex} \mathrm { F } \propto \frac { 1 } { \mathrm { r } ^ { 3 } } , {/tex} but
still remaining a central force. Then

Kepler's law of area still holds

B

Kepler's law of period still holds

C

Kepler's law of area and period still holds

D

neither the law of area nor the law of period still holds

Explanation

Q 17.    

Correct4

Incorrect-1

Four equal masses (each of mass M) are placed at the corners of a square of side a. The escape velocity of a body from the centre O of the square is

A

{tex} \sqrt [ 4 ] { \frac { 2 \mathrm { GM } } { \mathrm { a } } } {/tex}

{tex} \sqrt { \frac { 8 \sqrt { 2 } \mathrm { GM } } { \mathrm { a } } } {/tex}

C

{tex} \frac { 4 \mathrm { GM } } { \mathrm { a } } {/tex}

D

{tex} \sqrt { \frac { 4 \sqrt { 2 } \mathrm { GM } } { \mathrm { a } } } {/tex}

Explanation



Q 18.    

Correct4

Incorrect-1

If the gravitational force had varied as {tex} r ^ { - 5 / 2 } {/tex} instead of {tex} r ^ { - 2 } {/tex} ; the potential energy of a particle at a distance 'r' from the centre of the earth would be directly proportional to

A

{tex} r ^ { - 1 } {/tex}

B

{tex} r ^ { - 2 } {/tex}

{tex} r ^ { - 3 / 2 } {/tex}

D

{tex} r ^ { - 5 / 2 } {/tex}

Explanation





Q 19.    

Correct4

Incorrect-1

A particle of mass 'm' is kept at rest at a height 3R from the surface of earth, where 'R' is radius pf earth of 'M' is mass
of earth. The minimum speed with which it should be projected, so that it does not return back, is {tex} ( \mathrm { g } \text { is acceleration } {/tex} due to gravity on the surface of earth)

A

{tex} \left( \frac { G M } { R } \right) ^ { \frac { 1 } { 2 } } {/tex}

{tex} \left( \frac { G M } { 2 R } \right) ^ { \frac { 1 } { 2 } } {/tex}

C

{tex} \left( \frac { g R } { 4 } \right) ^ { \frac { 1 } { 2 } } {/tex}

D

{tex} \left( \frac { 2 g } { 4 } \right) ^ { \frac { 1 } { 2 } } {/tex}

Explanation

Q 20.    

Correct4

Incorrect-1

The ratio between the values of acceleration due to gravity at a height 1{tex} \mathrm { km } {/tex} above and at a depth of 1{tex} \mathrm { km } {/tex} below the Earth's surface is (radius of Earth is R)

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

B

{tex} \frac { R } { R - 1 } {/tex}

C

{tex} \frac { R - 2 } { R } {/tex}

D

1

Explanation





Q 21.    

Correct4

Incorrect-1

The weight of an object in the coal mine, sea level and at the top of the mountain, are respectively {tex} W _ { 1 } , W _ { 2 } {/tex} and {tex} W _ { 3 } {/tex} then

{tex} \mathrm { W } _ { 1 } < \mathrm { W } _ { 2 } > \mathrm { W } _ { 3 } {/tex}

B

{tex} \mathrm { W } _ { 1 } = \mathrm { W } _ { 2 } = \mathrm { W } _ { 3 } {/tex}

C

{tex} \mathrm { W } _ { 1 } < \mathrm { W } _ { 2 } < \mathrm { W } _ { 3 } {/tex}

D

{tex} \mathrm { W } _ { 1 } > \mathrm { W } _ { 2 } > \mathrm { W } _ { 3 } {/tex}

Explanation



Q 22.    

Correct4

Incorrect-1

The period of moon's rotation around the earth is nearly 29 days. If moon's mass were 2 fold its present value and all
other things remain unchanged, the period of moon's rotation would be nearly

A

29{tex} \sqrt { 2 } {/tex} days

B

29{tex} / \sqrt { 2 } {/tex} days

C

{tex} 29 \times 2 {/tex} days

29 days

Explanation

Q 23.    

Correct4

Incorrect-1

The mean radius of earth is {tex} R {/tex} , its angular speed on its own axis is {tex} \omega {/tex} and the acceleration due to gravity at earth's surface
is g. What will be the radius of the orbit of a geostationary satellite?

{tex} \left( R ^ { 2 } g / \omega ^ { 2 } \right) ^ { 1 / 3 } {/tex}

B

{tex} \left( R g / \omega ^ { 2 } \right) ^ { 1 / 3 } {/tex}

C

{tex} \left( R ^ { 2 } \omega ^ { 2 } / g \right) ^ { 1 / 3 } {/tex}

D

{tex} \left( R ^ { 2 } g / \omega \right) ^ { 1 / 3 } {/tex}

Explanation



Q 24.    

Correct4

Incorrect-1

In order to make the effective acceleration due to gravity equal to zero at the equator, the angular velocity of rotation
of the earth about its axis should be {tex} \left( g = 10 \mathrm { ms } ^ { - 2 } \text { and radius } \right. {/tex} of earth is 64000{tex} \mathrm { km } {/tex} )

A

Zero

{tex} \frac { 1 } { 800 } {/tex} rad {tex} \sec ^ { - 1 } {/tex}

C

{tex} \frac { 1 } { 80 } {/tex} rad {tex} \sec ^ { - 1 } {/tex}

D

{tex} \frac { 1 } { 8 } {/tex} rad {tex} \sec ^ { - 1 } {/tex}

Explanation



Q 25.    

Correct4

Incorrect-1

A body weighs 72{tex} \mathrm { N } {/tex} on the surface of the earth. What is the gravitational force on it due to earth at a height equal to half the radius of the earth from the surface?

32{tex} \mathrm { N } {/tex}

B

28{tex} \mathrm { N } {/tex}

C

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

D

72{tex} \mathrm { N } {/tex}

Explanation