**NEET Physics Chapter Wise Mock Test – Gravitation**

**Question 1:
**The magnitude of the force of gravity between two identical objects is given by F

_{0}. If the mass of each object is doubled but the distance between them is halved, then the new force of gravity between the object will be

(a) 16F

_{0}

(b) 4F

_{0}

(c) F

_{0}

(d) F

_{0}/2

**Question 2:
**

**Question 3:
**The distance of the centres of moon and earth is D. The mass of the earth is 81 times the mass of the moon. At what distance from the centre of the earth, the gravitational force on a particle will be zero?

(a) D/2

(b) 2D/3

(c) 4D/3

(d) 9D/10

**Question 4:
**

**Question 5:
**Two spheres of same size, one of mass 2 kg and another of mass 4 kg are dropped simultaneously from the top of Qutub Minar (height =72 m). When they are 1 m above the ground, the two spheres have the same

(a) momentum

(b) kinetic energy

(c) potential energy

(d) acceleration

**Question 6:
**

**Question 7:
**The weight of a body on the surface of the earth is 63 N. What is the gravitational force on it due to the earth at a height equal to half the radius of earth?

(a) 34 N

(b) 28 N

(c) 39 N

(d) 42 N

**Question 8:
**

**Question 9:
**The speed of earth’s rotation about its axis is co. Its speed is increased to x times to make the effective acceleration due to gravity equal to zero at the equator. Then, x is

(a) 1

(b) 8.5

(c) 17

(d) 34

**Question 10:
**Imagine a new planet having the same density as that of earth but it is 3 times bigger than the earth in size. If the acceleration due to gravity on the surface of earth is g and that on the surface of the new planet is g’, then .

(a) g’ = 3g

(b) g’ = g/9

(c) g’ = 9g

(d) g’ = 27g

**Question 11:
**

**Question 12:
**The density of newly discovered planet is twice that of earth. The acceleration due to gravity at the surface of the planet is equal to that at the surface of the earth. If the radius of the earth is R, the radius of the planet would be

(a) 2R

(b) 4R

(c) R/4

(d) R/2

**Question 13:
**If the distance between the earth and sun were half its present vdlue, the number of days in a year would have been

(a) 64.5

(b) 129

(c) 182.5

(d) 730

**Question 14:
**

**Question 15:
**A geostationary satellite orbits around the earth in a circular orbit of radius 36000 km. Then, the time period of a spy-satellite orbiting a few 100 km above the earth’s surface (R = 6400 km) will approximately be

(a) h/2

(b) 1 h

(c) 2 h

(d) 4 h

**Question 16:
**The ratio of mean distances of three planets from the sun are 0.5 :1:1.5, then the square of time periods are in the ratio of

(a) 1: 4 : 9

(b) 1:9:4

(c) 1:8:27

(d) 2 :1: 3

**Question 17:
**In a gravitational field, if a body is bound with the earth, then total mechanical energy has

(a) positive

(b) zero

(c) negative

(d) may be positive, negative or zero

**Question 18:
**When a body is lifted from surface of the earth to a height equal to the radius of the earth, then the change in its potential energy is

(a) mgR

(b) 2 mgR

(c) 1/2 mgR

(d) 4 mgR

**Question 19:
**

**Question 20:
**There is a crater of depth R/100 on the surface of the moon of radius R. A projectile is fired vertically upwards from the crater with a velocity equal to the escape velocity v from the surface of the moon. Maximum height attained by the projectile is

(a) 2R

(b) 99.5R

(c) R/2

(d) R/99.5

**Question 21:
**

**Question 22:
**An object of mass m is raised from the surface of the earth to a height equal to the radius of the earth, that is, taken from a distance R to 2R from the centre of the earth. What is the gain in its potential energy?

(a) 1/2 mgR

(b) 1/4 mgR

(c) 1/2 mgR2

(d) 1/6 mgR

**Question 23:
**

**Question 24:
**

**Question 25:
**

**Question 26:
**The velocity with which a projectile must be fired to escape from the earth does not depend upon

(a) mass of earth

(b) mass of projectile

(c) radius of earth

(d) None of these

**Question 27:
**

**Question 28:
**

**Question 29:
**Escape velocity on the earth is 11.2 kms

^{-1}. What would be the escape velocity on a planet whose mass is 1000 times and radius is 10 times that of earth?

(a) 112 kms

^{-1}

(b) 11.2 kms

^{-1}

(c) 1.12 kms

^{-1}

(d) 3.7 kms

^{-1}

**Question 30:
**

**Question 31:
**An earth satellite is moved from one stable circular orbit to another higher stable circular orbit. Which one of the following quantities increase for the satellite as a result of this change?

(a) Angular momentum

(b) Kinetic energy

(c) Angular velocity

(d) Linear orbital speed

**Question 32:
**

**Question 33:
**Two satellites of earth, S

_{1}and S

_{2}are moving in the same orbit. The mass of S

_{1}, is four times the mass of S

_{2}. Which one of the following statements is true?

(a) The time period of S

_{1}is four times that of S

_{1}

(b) The potential energies of earth and satellite in the two cases are equal

(c) S

_{1}and S

_{2}are moving with the same speed

(d) The kinetic energies of the two satellites are equal

**Question 34:
**

**Question 35:
**

**Question 36:
**A particle is fired vertically upwards with a speed of 15 kms

^{-1}from the surface of earth. The speed with which it moves in intersteller space, is

(take escape speed from surface of earth as 11.2 kms

^{-1})

(a) zero

(b) 3.8 kms

^{-1}

(c) ≅ 10 kms

^{-1}

(d) ≅ 4kms

^{-1}

**Question 37:
**

**Question 38:
**Network done on a satellite revolving in an elliptical orbit in one complete revolution

(a) is zero

(b) is non-zero

(c) may be zero

(d) None of these

**Question 39:
**

**Direction (Q. Nos. 40-45):** In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements, mark the correct answer as

(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

(b) If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion

(c) If Assertion is true but Reason is false

(d) If both Assertion and Reason are false

**Question 40:
Assertion (A): **Acceleration due to moon’s gravity on moon’s surface is g

_{e}/6 Acceleration due to earth’s

**gravity on moon’s surface is g**

_{e}/(60)

^{2}

**The distance of moon from earth’s centre is approximately equal to 60 times the radius of earth.**

Reason (R):

Reason (R):

**Question 41:
Assertion (A): **Due to binding energy of satellite, it is attached with the earth.

**Binding energy of the particle is given by**

Reason (R):

Reason (R):

BE = E = – GmM/R

**Question 42:
**

**Question 43:
Assertion (A): **Areal velocity of a planet around sun will become two times, if mass of planet is halved.

**Areal velocity = L/2m where L is angular momentum of planet about centre of sun.**

Reason (R):

Reason (R):

**Question 44:
**

**Question 45:
Assertion (A): **There is no effect of rotation of earth on acceleration due to gravity at poles.

**Rotation of earth is about polar axis.**

Reason (R):

Reason (R):

**Question 46:
**

**Question 47:
**If the value of g at the surface of the earth is 9.8 m/s

^{2}, then the value of g at a place 480 km above the surface of the earth will be (radius of the earth is 6400 km)

(a) 8.4 m/s

^{2}

(b) 9.8 m/s

^{2}

(c) 7.2 m/s

^{2}

(d) 4.2 m/s

^{2}

**Question 48:
**

**Question 49:
**

**Question 50:
**If the earth stops moving around its polar axis, then what will be effect on body placed at South axis?

(a) Remain same

(b) Increase

(c) Decrease but not zero

(d) Decrease and zero

**Question 51:
**The height at which the weight of a body becomes 1/16

^{th}, its weight on the surface of earth (radius R), is

(a) 5R

(b) 15R

(c) 3R

(d) 4R

**Question 52:
**

**Question 53:
**Assuming the earth to be a sphere of uniform mass density, how much would body weight half way down to the centre of earth, if it weighed 250N on the surface?

(a) 150 N

(b) 175 N

(c) 125N

(d) 200 N

**Question 54:
**The radii of circular orbits of two satellites A and B of the earth are 4R and R, respectively. If the speed of satellite A is 3v, then the speed of satellite B will be

(a) 3v/4

(b) 6v

(c) 12v

(d) 3v/2

**Question 55:
**A particle of mass M is situated at the centre of a spherical shell of same mass and radius a. The gravitational potential at a point situated at a/2 distance from the centre, will be

(a) -3GM/a

(b) -2GM/a

(c) -GM/a

(d) -4GM/a

**Question 56:
**Infinite number of bodies, each of mass 2 kg are situated on x-axis at distance 1 m, 2 m, 4 m, 8 m respectively from the origin. The resulting gravitational potential due to this system at the origin will be

(a) -G

(b) -8G/3

(c) -4G/3

(d) -4G

**Question 57:
**A body of mass m taken from the earth’s surface to the height equal to twice the radius (R) of the earth. The change is potential energy of body will be

(a) mg 2R

(b) -2mgR/3

(c) 3 mgR

(d) mgR/3

**Question 58:
**

**Question 59:
**A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass =5.98×10

^{24}kg) have to be compressed to a black hole?

(a) 10

^{-9}m

(b) 10

^{-6}m

(c) 10

^{-2}m

(d) 100m

**Question 60:
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