JEE Physics Gravitation MCQs Set B

Question. The orbital speed of a satellite revolving around a planet in a circular orbit is v₀. If its speed is increased by 10%, then
(a) It will start rotating in an elliptical orbit
(b) It will escape from its orbit
(c) It will continue to move in the same orbit
(d) It will move in a circular orbit of radius 20% more then radius of initial orbit

Answer: A

Question. When energy of a satellite-planet system is positive then satellite will
(a) When energy of a satellite-planet system is positive then satellite will
(b) Escape out with minimum speed
(c) Move around planet in elliptical orbit
(d) Move around planet in circular orbit

Answer: A

Question. If radius of an orbiting satellite is decreased, then its kinetic energy
(a) Increases and potential energy decreases
(b) And potential energy increase
(c) And potential energy decrease
(d) Decreases and potential energy increases

Answer: C

Question. At what altitude (h) above the earth’s surface would the acceleration due to gravity be one fourth of its value at the earth’s surface?
(a) h = R
(b) h = 4R
(c) h = 2R
(d) h = 16R

Answer: A

Question. The radius of earth is about 6400 km and that of Mars is 3200 km. The mass of the earth is about 10 times the mass of Mars. An object weighs 200 N on the surface of Earth. Its weight on the surface of mars will be
(a) 80 N
(b) 40 N
(c) 8 N
(d) 20 N

Answer: A

Question. The earth (mass = 6 × 10²⁴ kg) revolves around the sun with an angular velocity of 2 × 10^–7 rad/s in a circular orbit of radius 1.5 × 10⁸ km. The force exerted by the sun on the earth, in newtons, is
(a) 36 × 10²¹
(b) 27 × 10³⁹
(c) Zero
(d) 18 × 10²⁵

Answer: A

Question. The period of revolution of planet A around the sun is 8 times that of B. The distance of A from the sun is how many times greater than that of B from the sun?
(a) 4
(b) 5
(c) 2
(d) 3

Answer: A

Question. The escape velocity of a body on the surface of the earth is 11.2 km/s. If the earth’s mass increases to twice its present value and radius of the earth becomes half, the escape velocity becomes
(a) 22.4 km/s
(b) 44.8 km/s
(c) 5.6 km/s
(d) 11.2 km/s

Answer: A

Question. A body of weight 72 N moves from the surface of earth at a height half of the radius of earth, then gravitational force exerted on it will be
(a) 32 N
(b) 36 N
(c) 144 N
(d) 50 N

Answer: A

Question. A planet has mass equal to mass of the earth but radius one fourth of radius of the earth. Then escape velocity at the surface of this planet will be
(a) 22.4 km/s
(b) 11.2 km/s
(c) 5.6 km/s
(d) 44.8 km/s

Answer: A

Question. The acceleration due to gravity on a planet A is 9 times the acceleration due to gravity on planet B. A man jumps to a height of 2 m on the surface of A. What is the height of jump by the same person on the planet B?
(a) 18 m
(b) 2/9 m
(c) 6 m
(d) 2/3 m

Answer: A

Question. Two spheres of masses m and M are situated in air and the gravitational force between them is F. The space around the masses is now filled with a liquid of specific gravity 3. The gravitational force will now be
(a) F
(b) 3F
(c) F / 3
(d) F / 9

Answer: A

Question. A ball is dropped from a spacecraft revolving around the earth at a 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 go very far in the space
(d) It will fall down to the earth gradually

Answer: A