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

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Gravitation

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Q 1. A solid sphere of uniform density and radius R applies a gravitational force of attraction equal to F1 on a particle placed at A, distance 2R from the centre of the sphere.


A spherical cavity of radius {tex} \frac {R}{2} {/tex} is now made in the sphere as shown in the figure. The particle with cavity now applies a gravitational force F2 on the same particle placed at A . The ratio {tex} \frac {{ F } _ { 2 }}{{ F } _ { 1 }} {/tex} will be

A

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

B

{tex} 3 {/tex}

C

{tex} 7 {/tex}

{tex}\frac {7}{9} {/tex}

Explanation

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Q 2. 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 ) \mathrm { mv } ^ { 2 } {/tex}

Explanation

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Q 3. 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

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Q 4. 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



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Q 5. 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

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Q 6. 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



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Q 7. 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 '{tex} r {/tex}' 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



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Q 8. 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





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Q 9. 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



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Q 10. 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

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Q 11. 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