JEE Physics Gravitation MCQs Set C

Question. The mass of the Jupiter is 1.9 × 10²⁷ kg and that of the sun is 1.99 × 10³⁸ kg. The mean distance of the Jupiter from the sun is 7.8 × 10¹¹ m. Speed of the Jupiter is (assuming that Jupiter moves in a circular orbit around the sun)
(A) 1.304 × 10⁴ m/sec
(B) 13.04 × 10⁴ m/sec
(C) 1.304 × 106 m/sec
(D) 1.304 × 102 m/sec

Answer : A

Question. The acceleration due to gravity
(A) has the same value everywhere in space
(B) has the same value everywhere on the earth
(C) varies with the latitude on the earth
(D) is greater on the moon due to its smaller diameter

Answer : C

Question. SI unit of weight is
(A) kg wt
(B) N
(C) g wt
(D) none of these

Answer : B

Question. Gravitational force which acts on 1 kg is
(A) 9.8 N
(B) 1/ 9.8 N
(C) 980 N
(D) none of these

Answer : A

Question. Weight is
(A) measured by a spring balance
(B) measured by a beam balance
(C) measured in kg
(D) a scalar quantity

Answer : A

Question. A satellite which is geostationary in a particular orbit is taken to another orbit. Its distance from the centre of earth in new orbit is 2 times than that of the earlier orbit. The time period in the second orbit is
(A) 4.8 hours
(B) 48 √2 hours
(C) 24 hours
(D) 24 √2 hours

Answer : D

Question. Two metal spheres of equal radius r are touching each other. The force of attraction F between them is
(A) F ∝ r⁴
(B) F ∝ r⁶
(C) F ∝ r²
(D) F ∝ 1/r²

Answer : A

Question. A man weighs 60 kg at earth's surface. At what height above the earth's surface his weight becomes 30 kg? (radius of earth = 6400 km).
(A) 1624 km
(B) 2424 km
(C) 2624 km
(D) 2826 km

Answer : C

Question. There are two bodies of masses 100 kg and 10000 kg separated by a distance 1m. At what distance from the smaller body, intensity of gravitational field will be zero?
(A) 1/9 m
(B) 1/10 m
(C) 1/11 m
(D) 10 /11 m

Answer : C

Question. At what height, is the value of g half that on the surface of earth? (R = radius of the earth)
(A) 0.414R
(B) R
(C) 2R
(D) 3.5R

Answer : A

Question. A planet of mass m moves around the sun of mass M in an elliptical orbit. The maximum and minimum distances of the planet from the sun are r₁ and r₂ respectively. The time period ofthe planet is proportional to.
(A) r₁^3/2
(B) r₂^3/2
(C) {(r₁+r₂)/2}^3/2
(D) {r₁+r₂)/2}^3/2

Answer : C

Question. On a planet (whose size is the same and mass 4 times as that of the earth), the energy needed to lift a 2 kg mass vertically upwards through 2 m distance on the planet is (g = 10 m/s² on the surface of the earth)
(A) 16 joules
(B) 160 joules
(C) 32 joules
(D) 320 joules

Answer : B

Question. A satellite is revolving in a circular orbit at a distance of 2620 km from the surface of the earth. The time period of revolution of the satellite is (Radius of the earth = 6380 km, mass of the earth = 6 × 10²⁴ kg, G = 6.67 × 10^–11 N-m²/kg²)
(A) 2.35 hours
(B) 23.5 hours
(C) 3.25 hours
(D) 32.5 hours

Answer : A

Question. On the surface of the earth, force of gravitational attraction between two masses kept at distance d apart is 6 Newtons. If these two masses are taken to the surface of the moon and kept at the same distance d, the force between them will be.
(A) 1N
(B) 36N
(C) 1/6 N
(D) 6N

Answer : D

Question. Time period of simple pendulum in a satellite is
(A) infinite
(B) zero
(C) 2 sec
(D) cannot be calculated

Answer : A

Question. A ball is dropped from a spacecraft revolving around the earth at height of 120 km. What will happen to the ball ?
(A) It will continue to move with the same speed along the original orbit of spacecraft
(B) It will move with the same speed, tangentially to the spacecraft
(C) It will fall down to the earth gradually
(D) It will go very far in space

Answer : A

Question. The value of the acceleration due to gravity at a height of 12,800 km from the surface of the earth (R_e = 6400 km) g' = g (R/R+h)² is :-
(A) 3.09 m/s²
(B) 1.09 m/s²
(C) 4.08 m/s²
(D) 5.07 m/s²

Answer : B

Question. The weight of a body of mass 5 kg is :-
(A) 69.0 N
(B) 79.0 N
(C) 49.0 N
(D) 39.0 N

Answer : C

Question. The weight of the body at the surface of the earth is 20 N and the radius of the earth is 6400 km. The weight of a body at a height 6400 km above is :-
(A) 7 N
(B) 5 N
(C) 4 N
(D) 6 N

Answer : B

Question. Consider a heavenly body which has a mass twice that of the earth and a radius thrice that of the earth. The weight of a book on this heavenly body, if its weight on the earth is 900 N will be :-
(A) 400 N
(B) 600 N
(C) 500 N
(D) 200 N

Answer : D

Question. Two protons are kept at a separation of 1 femtometre (1 femtometre = 10^–15 m). The mass of a proton is 1.67 × ¹⁰kg. The gravitational force between them is :-
(A) 1.86 × 10^–34 N
(B) 5.86 × 10^–34 N
(C) 2.8 × 10^–34 N
(D) 4.86 × 10^–34 N

Answer : A

Question. The mass of the sun is 2.0 × 10³⁶ kg and that of the earth is 6.0 × 10²⁴ kg. The distance between the sun and the earth is 1.5 × 10¹¹ m. The gravitational force between the sun and earth is :-
(A) 3.56 × 10²⁸ N
(B) 4.56 × 10²⁸ N
(C) 6.56 × 10²⁸ N
(D) 5.56 × 10²⁸ N

Answer : A

Question. A particle is taken to a height of 2Re above the earth's surface, where Re is the radius of the earth. If it is dropped from this height, its acceleration is will be :-
(A) 3.1 m/s²
(B) 5.1 m/s²
(C) 1.1 m/s²
(D) 2.1 m/s²

Answer : C

Question. Consider a heavenly body whose mass is 3 × 10²⁴ kg (half of that of the earth) and radius is 3200 km (half of that of the earth). The acceleratin due to gravity at the surface of this heavenly body will be :-
(A) 39.6 m/s²
(B) 19.6 m/s²
(C) 29.6 m/s²
(D) 49.6 m/s²

Answer : B

Question. Two bodies of masses 1 kg and 2 kg respectively are placed at a separation of 1 m. Find the accelerations of the bodies assuming that only gravitational force acts between them :-
(A) 1.33 × 10^–10 & 6.67 × 10^–11 m/s²
(B) 1.33 × 10^–11 & 6.25 × 10^–11 m/s²
(C) 5.36 × 10^–11 & 5.26 × 10^–11 m/s²
(D) 3.11 × 10^–11 & 5.26 × 10^–11 m/s²

Answer : A

Question. Communication satellites move in the orbits of radius 44,400 km around the earth. The acceleration of such a satellite assuming that the only force acting on it is that due to the earth is :-
(A) 0.4 m/s²
(B) 0.6 m/s²
(C) 0.2 m/s²
(D) 0.1 m/s²

Answer : C

Question. Two persons weighing 50 kg and 60 kg are seated across a table. If they are one metre apart, the gravitational force between them is :-
(A) 5 × 10^–7 N
(B) 2 × 10^–7 N
(C) 4 × 10^–7 N
(D) 3 × 10^–7 N

Answer : B

Question. The mass of a planet is twice and its radius is 3 times that of the earth. The weight of a body, which has a mass of 5 kg on the surface of the earth, on that planet is :-
(A) 11.95 N
(B) 20.9 N
(C) 10.85 N
(D) 9.9 N

Answer : C

Question. The height at which a body has one fourth of its weight when it is on the surface of the earth is :-
(A) At a height r where r is the radius of the earth
(B) At a height 2r where r is the radius of the earth
(C) At a height r/2 where r is the radius of the earth
(D) At a height r/4 where r is the radius of the earth

Answer : A

Question. A space vehicle is moving vertically upward with a constant acceleration 'a'. An astronaut of weight 'mg' feels heavier. When will the astronants weight becomes 2 mg ?
(A) a = 2g
(B) a = g/2
(C) a = g
(D) a = 3g

Answer : C

Question. Two bodies A and B of masses 100 g and 200 g respectively are dropped near the earth's surface. Let the accelerations of A and B be 'a₁ ' and 'a₂ ' respectively. Then :
(A) a₁ = a₂
(B) a₁ < a₂
(C) a₁ > a₂
(D) a₁ ≠ a₂

Answer : A

Question. At what height will a man's weight be half his weight on the surface of earth ? (R is the radius of earth)
(A) 0.214 R
(B) 0.514 R
(C) 0.414 R
(D) 0.516 R

Answer : C

Question. If the radius of the earth were to be increased by a factor of 3, by what factor would its density have to be changed to keep 'g' the same ?
(A) 3
(B) 1/3
(C) 6
(D) 1/6

Answer : B