# MCQ | Gravitation

Quiz TEST – I

Question:1. The ratio of the inertial mass to gravitational mass is equal to

(A) 0.5

(B) 1

(C) 2

(D) no fixed number.

Ans: (B)

Question:2. If the radius of earth were to shrink by one percent, its mass remaining the same, the acceleration due to gravity on the earth’s surface would

(A) decrease

(B) remains unchanged

(C) increase.

(D) none of these

Ans: (C)

Question:3.  Kepler’s third law of planetary motion provides information about

(A) areal velocity of a planet

(B) nature of motion of a planet

(C) ratio of time periods of two planets

(D) all the above

Ans: (C)

Question:4. If a particle is slowly brought from reference point to another point P in a gravitational field, then work done per unit mass by the external agent is (at that point)

(A) gravitational force

(B) gravitational field intensity

(C) gravitation potential

(D) none of the above

Ans: (C)

Question:5.  The atmosphere is held to the earth by

(A) winds

(B) gravity

(C) clouds

(D) none of the above.

Ans: (B)

Question:6.  The time period of simple pendulum of infinite length is

(A) infinite

(B) 2π√(R/g)

(C) 2π√(g/R)

(D) (1/2π)√(R/g)

Ans: (B)

Question:7. When a satellite has an elliptical orbit, the plane of the orbit

(A) sometimes passes through the centre of earth

(B) does not pass through the centre of earth

(C) passes through the centre of earth always

(D) none of the above.

Ans: (C)

Question:8. The earth revolves round the sun in an elliptical orbit. Its speed is

(A) going on decreasing continuously

(B) greatest when it is closest to the sun

(C) greatest when it is farthest from the sun

(D) constant at all the points on the orbit.

Ans: (B)

Question:9 Two satellites of masses m1 and m2 (m1 > m2) are revolving round the earth in circular orbits of radii r1 and r2 (r1 > r2) respectively. Which of the following statements is true regarding their speeds v1 and v2 ?

(A) v1 = v2

(B) v1 < v2

(C) v1 > v2

(D) (v1/r1) = (v2/r2)

Ans: (B)

Question:10.  Two satellites are orbiting around the earth in circular orbits of same radius. One of them is 10 times greater in mass than the other. Their period of revolutions are in the ratio

(A) 100:1

(B) 1:100

(C) 10:1

(D) 1:1

Ans: (D)

Question:11.  A person brings a mass of 1 kg from infinity to a point A. Initially the mass was at rest but it moves at a speed of 2 m/s as it reaches A. The work done by a person on the mass is –3J. The potential at A is:

(A) -3 J/kg

(B) -2 J/kg

(C) -5 J/kg

(D) none of these.

Ans: (C)

Question:12.  Let V and E be the gravitational potential and gravitational field at a distance r from the centre of a uniform spherical shell. Consider the following two statements, (A) The plot of V against r is discontinuous and (B) The plot of E against r is discontinuous.

(A) Both A and B are correct

(B) A is correct but B is wrong

(C) B is correct but A is wrong

(D) both A and B are wrong.

Ans: (C)

Question:13.  Two satellites A and B move round the earth in the same orbit. The mass of B is twice the mass of A. Which of the following is correct?

(A) Speeds of A and B are equal

(B) The potential energy of earth + A is same as that of earth + B

(C) The kinetic energy of A and B are equal

(D) The total energy of earth + A is same as that of earth + B.

Ans: (A)

Question:14.  The minimum speed of a particle projected from earth’s surface so that it will never return is/are

(A) √(GM/R)

(B) 22.1 km/sec

(C) √(4goR)

(D) none of above

Ans: (D)

Question:15.  A body of mass m is approaching towards the centre of a hypothetical hollow planet of mass M and radius R. The speed of the body when it passes the centre of the planet through a diametrical tunnel is

(A) √(GM/R)

(B) √(2GM/R)

(C) Zero

(D) none of these.

Ans: (B)

Question:16.  The energy required to remove a body of mass m from earth’s surface is/are equal t

(A) -GMm/R

(B) mgR

(C) -mgR

(D) none of these.

Ans: (B)

Question:17. A small mass ‘m’ is moved slowly from the surface of earth to a height ‘h’ from the surface. The work done (by external agent) in doing this is

(A) mgh, for all values of h.

(B) – mgh, for h << R

(C) (1/2)mgR for h = R

(D) -(1/2)mgR , for h = R

Ans: (C)

Question:18.  The escape velocity of a particle of mass m varies as:

(A) m2

(B) m

(C) m0

(D) m-1

Ans: (C)

Question:19.  Two particles of masses m1 & m2 are infinitely separated and their gravitational potential energy is chosen zero. Their gravitational energy, when they are separated by r, is

(A) Gm1m2/r2

(B) Gm1m2/r

(C) -Gm1m2/r2

(D) Gm1m2/r

Ans: (D)

Question:20. The gravitational field at a point on the axis of a uniform disc,
(mass = M, radius = a) forming θ at the point, is

(A) (GM/a)cosθ

(B) (GM/a)(1-cosθ)

(C) (2GM/a2)(1-cosθ)

(D) (2GM/a2)(1-sinθ)