JEE Physics Gravitation MCQs Set A

Question: According to Kepler, planets move in

• a) Elliptical orbits around the sun with sun at one of its foci
• b) Straight lines with constant velocity
• c) Elliptical orbits around the sun with sun at exact centre
• d) Circular orbits around the sun

Answer: Elliptical orbits around the sun with sun at one of its foci

Question: The minimum and maximum distances of a planet revolving around sun are r and R. If the minimum speed of planet on its trajectory is v₀, its maximum speed will be

• a)

  

• b)

  

• c)

  

Answer:

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 of the planet is proportional to

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: In a satellite if the time of revolution is T, then PE is proportional to

• a) T^–2/3
• b) T^–4/3
• c) T³
• d) T^1/3

Answer: T^–2/3

Question: The torque on a planet about the centre of sun is

• a) Zero
• b) Positive
• c) Negative
• d) Depend on mass of planet

Answer: Zero

Question: During motion of a planet from perihelion to aphelion the work done by gravitational force of sun on it is

• a) Negative
• b) May be positive or negative
• c) Zero
• d) Positive

Answer: Negative

Question: The gravitational constant depends upon

• a) None of these
• b) Gravitational mass
• c) Size of the bodies
• d) Distance between the bodies

Answer: None of these

Question: Gravitation is the phenomenon of interaction between

• a) Any arbitrary shaped masses
• b) Point masses only
• c) Planets only
• d) None of these

Answer: Any arbitrary shaped masses

Question: Force of gravitation between two masses is found to be F, in vacuum. If both the masses are dipped in water at same distance then, new force will be

• a) F
• b) Cannot say
• c) < F
• d) > F

Answer: F

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d) Gm²

Answer:

Question: Three particles A, B and C each of mass m are lying at the corners of an equilateral triangle of side L. If the particle A is released keeping the particles B and C fixed, the magnitude of instantaneous acceleration of A is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  Two planets have same density but different radii. The acceleration due to gravity would be

• a) Greater on the larger planet
• b) Same on both planets
• c) Greater on the smaller planet
• d) Dependent on the distance of planet from the sun

Answer: Greater on the larger planet

Question: If the radius of earth shrinks by 1.5% (mass remaining same), then the value of gravitational acceleration changes by

• a) 3%
• b) –3%
• c) –2%
• d) 2%

Answer: 3%

Question: At what height above the surface of earth the value of "g" decreases by 2%? [radius of the earth is 6400 km]

• a) 64 km
• b) 128 km
• c) 1600 km
• d) 32 km

Answer: 64 km

Question: During motion of a man from equator to pole of earth, its weight will (neglect the effect of change in the radius of earth)

• a) Increase by 0.34%
• b) Increase by 0.52%
• c) Decrease by 0.34%
• d) Decrease by 0.52%

Answer:  Increase by 0.34%

Question:  If density of a planet is double that of the earth and the radius 1.5 times that of the earth, the acceleration due to gravity on the surface of the planet is

• a) 3 times that on the surface of the earth
• b) 6 times that on the surface of the earth
• c)

  

• d)

  

Answer: 3 times that on the surface of the earth

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: If R is the radius of earth and g is the acceleration due to gravity on the earth’s surface. Then mean density of earth is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The value of g at the surface of earth is 9.8 m/s². Then the value of ‘g’ at a place 480 km above the surface of the earth will be nearly (radius of the earth is 6400 km)

• a) 8.5 m/s²
• b) 4.2 m/s²
• c) 7.2 m/s²
• d) 9.8 m/s²

Answer: 4.2 m/s²

Question: The value of g at the surface of earth is 9.8 m/s². Then the value of ‘g’ at a place 480 km above the surface of the earth will be nearly (radius of the earth is 6400 km)

• a) 8.5 m/s²
• b) 4.2 m/s²
• c) 7.2 m/s²
• d) 9.8 m/s²

Answer: 8.5 m/s²

Question: If the change in the value of ‘g’ at a height ‘h’ above the surface of the earth is same as at a depth x below it, then (x and h being much smaller than the radius of the earth)

• a) x = 2h
• b) x = h
• c)

  

• d) x = h²

Answer: x = 2h

Question: As we go from the equator to the poles, value of ‘g’

• a) Increases
• b) Decreases
• c) Remains the same
• d) First increase and then decrease

Answer: Increases

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The acceleration due to gravity on a planet is 1.96 m/s². If it is safe to jump from a height of 3 m on the earth, the corresponding height on the planet will be

• a) 15 m
• b) 9 m
• c) 6 m
• d) 3 m

Answer: 15 m

Question: Which of the following graph represents the variations of acceleration due to gravity(g) with distance r from the centre of earth?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: An object is taken to height 2R above the surface of earth, the increase in potential energy is [R is radius of earth]

• a)

  

• b)

  

• c)

  

• d) 2 mgR

Answer:

Question: The change in potential energy when a body of mass m is raised to height nR from the earth’s surface is (R is radius of earth)

• a)

  

• b)

  

• c)

  

• d) nmgR

Answer:

Question: A stationary object is released from a point P at a distance 3R from the centre of the moon which has radius R and mass M. Which of the following gives the speed of the object on hitting the moon?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Four particles A, B, C and D each of mass m are kept at the corners of a square of side L. Now the particle D is taken to infinity by an external agent keeping the other particles fixed at their respective positions. The work done by the gravitational force acting on the particle D during its movement is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: If an object is projected vertically upwards with speed, half the escape speed of earth, then the maximum height attained by it is [R is radius of earth]

• a)

  

• b) 2 R
• c)

  

• d) R

Answer:

Question: The total mechanical energy of an object of mass m projected from surface of earth with escape speed is

• a) Zero
• b) Infinite
• c)

  

• d)

  

Answer: Zero

Question: A body is thrown with a velocity equal to n times the escape velocity (v_e). Velocity of the body at a large distance away will be

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question: The escape velocity of a body from earth is about 11.2 km/s. Assuming the mass and radius of the earth to be about 81 and 4 times the mass and radius of the moon, the escape velocity in km/s from the surface of the moon will be

• a) 2.48
• b) 11
• c) 49.5
• d) 0.54

Answer: 2.48

Question: If M is mass of a planet and R is its radius then in order to become black hole [c is speed of light]

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The atmosphere on a planet is possible only if [where v_rmsis root mean square speed of gas molecules on planet and v_e is escape speed on its surface]

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A small satellite is revolving near earth’s surface. Its orbital velocity will be nearly

• a) 8 km/s
• b) 11.2 km/s
• c) 4 km/s
• d) 6 km/s

Answer: 8 km/s

Question: The time period of a satellite in a circular orbit of radius R is T. The period of another satellite in a circular orbit of radius 4R is

• a) 8T
• b) 8T
• c)

  

• d)

  

Answer: 8T

Question: When speed of a satellite is increased by x percentage, it will escape from its orbit, where the value of x is

• a) 41.4%
• b) 27.5%
• c) 34.4%
• d) 11.2%

Answer: 41.4%

Question: If potential energy of a satellite is –2MJ, then the binding energy of satellite is

• a) 1 MJ
• b) 2 MJ
• c) 8 MJ
• d) 4 MJ

Answer: 1 MJ

Question: The time period of polar satellites is about

• a) 100 min
• b) 84.6 min
• c) 6 hr
• d) 24 hr

Answer: 100 min

Question: If a satellite of mass 400 kg revolves around the earth in an orbit with speed 200 m/s then its potential energy is

• a) –16 MJ
• b) –2.4 MJ
• c) –8.0 MJ
• d) –1.2 MJ

Answer: –16 MJ

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A satellite of the earth is revolving in a circular orbit with a uniform speed v. If the gravitational force suddenly disappears, the satellite will

• a) Move with a velocity v, tangentially to the original orbit
• b) Continue to move with velocity v along the original orbit
• c) Fall down with increasing velocity
• d) Ultimately come to rest somewhere on the original orbit

Answer: Move with a velocity v, tangentially to the original orbit

Question: The relay satellite transmits the television signals continuously from one part of the world to another because its

• a) Period is equal to the period of rotation of the earth about its axis
• b) Period has no relation with the period of the earth about its axis
• c) Period is less than the period of rotation of the earth
• d) Period is greater than the period of rotation of the earth

Answer: Period is equal to the period of rotation of the earth about its axis

Question: If height of a satellite from the surface of earth is increased, then its

• a) All of these
• b) Kinetic energy will decrease
• c) Potential energy will increase
• d) Total energy will increase

Answer: All of these

Question: The gravitational force on a body of mass 1.5 kg situated at a point is 45 N. The gravitational field intensity at that point is

• a) 30 N/kg
• b) 67.5 N/kg
• c) 46.5 N/kg
• d) 43.5 N/kg

Answer: 30 N/kg

Question: A uniform sphere of mass M and radius R is surrounded by a concentric spherical shell of same mass but radius 2R. A point mass m is kept at a distance x (>R) in the region bounded by spheres as shown in the figure. The net gravitational force on the particle is

• a)

  

• b)

  

• c)

  

• d) Zero

Answer:

Question: If the gravitational potential on the surface of earth is V₀, then potential at a point at height half of the radius of earth is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Two point masses having mass m and 2m are placed at distance d. The point on the line joining point masses, where gravitational field intensity is zero will be at distance

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The ratio of kinetic energy of a planet at perigee and apogee during its motion around the sun in elliptical orbit of eccentricity e is

• a)

  

• b)

  

• c)

  

• d) 1 : e

Answer:

Question: An earth satellite X is revolving around earth in an orbit whose radius is one-fourth of the radius of orbit of a communication satellite. Time period of revolution of X is

• a) 3 hrs
• b) 6 hrs
• c) 4 days
• d) 72 days

Answer: 3 hrs

Question: Two satellites of equal mass are revolving around earth in elliptical orbits of different semi-major axis. If their angular momenta about earth centre are in the ratio 3 : 4 then ratio of their areal velocity is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: When a satellite moves around the earth in a certain orbit, the quantity which remains constant is

• a) Areal velocity
• b) Potential energy
• c) Kinetic energy
• d) Angular velocity

Answer: Areal velocity

Question: Consider a planet moving around a star in an elliptical orbit with period T. The area of the elliptical orbit is proportional to

• a)

  

• b)

  

• c)

  

• d) T

Answer:

Question: A body weighs 72 N on surface of the earth. When it is taken to a height of h = 2R, where R is radius of earth, it would weigh

• a) 8 N
• b) 9 N
• c) 18 N
• d) 36 N

Answer: 8 N

Question: If all objects on the equator of earth feel weightless then the duration of the day will nearly become

• a) 1.41 hr
• b) 2.2 hr
• c) 4.4 hr
• d) 6.2 hr

Answer: 1.41 hr

Question:

• a) R
• b)

  

• c)

  

• d)

  

Answer: R

Question: If the gravitational potential energy of two point masses infinitely away is taken to be zero then gravitational potential energy of a galaxy is

• a) Negative
• b) Positive
• c) Zero
• d) Can have any value

Answer: Negative

Question: A particle of mass m is dropped from a height R equal to the radius of the earth above the tunnel dug through the earth as shown in the figure. Hence the correct statement is

• a) Both
• b) Particle will oscillate through the earth to a height h = R on both sides
• c) Motion of the particle is periodic
• d) Nome of this

Answer: Both