# MCQ Questions for Class 11 Physics Chapter 8 Gravitation with Answers

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## Gravitation Class 11 MCQs Questions with Answers

Multiple Choice Type Questions

Question 1.
If the density of Earth is doubled keeping its radius constant then acceleration due to gravity will become (the present value is 9,8 ms-2)
(a) 9.8 ms-2
(b) 4.9 ms-2
(c) 19.6 ms-2
(d) 2.45 ms-2

Answer: (c) 19.6 ms-2

Question 2.
A satellite is orbiting around the Earth with a period T. If the Earth suddenly shrinks to half its radius without change in mass, the period of revolution of the satellite will be
(a) T
(b) $$\frac {T}{2}$$
(c) $$\frac {T}{√2}$$
(d) 2T

Question 3.
Two satellites of mass m, and 10m, are put in the same orbit around the sun. If T1 and T2 be their time periods, then $$\frac {T_1}{T_2}$$ =
(a) 4
(b) 1
(c) $$\frac {1}{2}$$
(d) $$\frac {1}{4}$$

Question 4.
A projectle is fired with a velocity less than the escape velocity. What can we say about the sum of its potential and kinetic energies?
(a) Negative
(b) Positive
(c) Zero
(d) May be +ve, -ve or zero

Question 5.
The acceleration due to gravity’ increases by 0.5% when we go from equator to poles. What will be the time period of the pendulum at the equator which beats seconds at the poles?
(a) 1.950 s
(b) 1.995 s
(c) 2.050 s
(d) 2.005 s

Answer: (d) 2.005 s

Question 6.
At what height above the surface of Earth of radius R will the acceleration due to gravity be reduced by 0.1%?
(a) $$\frac {R}{100}$$
(b) $$\frac {R}{200}$$
(c) $$\frac {R}{1000}$$
(d) $$\frac {R}{2000}$$

Answer: (d) $$\frac {R}{2000}$$

Question 7.
A bail of weight W is thrown vertically upwards. The apparent w eight during the upward motion will be
(a) zero
(b) more than W
(c) less than W
(d) W

Question 8.
The acceleration due to gravity at a place is g. A ball of density ρ is gently released in a fluid of density σ. The downward acceleration of the ball if ρ > σ will be
(a) g
(b) g$$\frac {σ}{ρ}$$
(c) g($$\frac {1-σ}{ρ}$$)
(d) $$\sqrt{(1-\frac {ρ}{σ}})$$

Answer: (c) g($$\frac {1-σ}{ρ}$$)

Question 9.
The time period (T) of the artificial setelllite of Earth depends on the density (p) of the Earth as
(a) T ∝ r
(b) T ∝ $$\frac {1}{ρ}$$
(c) T ∝ $$\frac {1}{√ρ}$$
(d) T ∝ √ρ

Answer: (c) T ∝ $$\frac {1}{√ρ}$$

Question 10.
How much work per kilogram need to be done to shift a 1kg mass from the surface of Earth of infinity? Take acceleration due to gravity = g and radius of the Earth = R.
(a) gR
(b) $$\frac {R}{g}$$
(c) $$\frac {g}{R^2}$$
(d) $$\frac {g}{R}$$

Question 11.
What percentage of the potential energy is gained by the body in rising through a height equal to the radius of the Earth assuming that the gravitational potential energy of a body infinite distance away from Earth is zero.
(a) 1%
(b) 10%
(c) 50%
(d) 20%

Question 12.
A person on the moon can jump higher than on the Earth as
(а) the moon has rough surface.
(b) the moon is cooler than Earth.
(c) the value of ‘g’ on the moon is smaller than that on the Earth.
(d) there is almost no atmosphere on the moon.

Answer: (c) the value of ‘g’ on the moon is smaller than that on the Earth.

Question 13.
The gravitational pull on two bodies is 6.67 × 10-11 Nm²kg-2 in vacuum. The value of the gravitational pull in a dense matter of density 1016 kg m-3 will be
(a) 6.67 × 10-11 Nm² kg-2
(b) 6.67 × 10-21 Nm² kg-2
(c) 1.3 × 10-10 Nm² kg-2
(d) 6.67 × 10-1 Nm² kg-2

Answer: (a) 6.67 × 10-11 Nm² kg-2

Question 14.
Which of the following is the evidence to show that there must be a force acting on Earth directed towards the Sun.
(a) revolution of Earth around the Sun.
(b) apparent motion of Sun around the Earth.
(c) duration of falling bodies towards Earth.
(d) phenomenon of day and night.

Answer: (a) revolution of Earth around the Sun.

Question 15.
In order to find the time, the astronaut orbiting in an Earth satellite should use:
(а) a pendulum clock.
(b) a watch having a hair spring to keep it going.
(c) either a pendulum clock or a watch.
(d) neither a pendulum clock nor a watch.

Answer: (b) a watch having a hair spring to keep it going.

Question 16.
The orbital speed of Jupiter is
(a) less than the orbital speed of Earth.
(b) greater than the orbital speed of Earth.
(c) equal to the orbital speed of Earth.
(d) zero.

Answer: (a) less than the orbital speed of Earth.

Question 17.
Weightlessness experienced while orbiting the earth in spaceship, is the result of:
(a) zero gravity
(b) centre of gravity
(c) inertia
(d) acceleration

Question 18.
The sky appears black to an astronaut in a spaceship. It is so because:
(a) surrounding medium absorbs sky light.
(b) the region has only invisible part (UV and IR) of Sun light.
(c) surrounding has no atmosphere.
(d) none of the above.

Answer: (c) surrounding has no atmosphere.

Question 19.
A satellite appears to be at rest when seen from the equator. Its height from the Earth’s surface is nearly
(a) 6400 km
(b) 32000 km
(c) 35800 km
(d) 358000 km

Answer: (c) 35800 km

Question 20.
The time period of a satellite revolving round the Earth at a height h from the Earth’s surface is given by
(a) 2π $$\sqrt{\frac {R^3}{GM}}$$
(b) 2π $$\sqrt{\frac {GM}{R^3}}$$
(c) 2π $$\sqrt {GMR^3}$$
(d) 2π $$\sqrt{\frac {(R+h)^3}{GM}}$$

Answer: (d) 2π $$\sqrt{\frac {(R+h)^3}{GM}}$$

Fill in the blanks

Question 1.
Two planets are at distances R1 and R2 from the Sun. Then the ratio of their period will be ………………..

Answer: ($$\frac {R_1}{R_2}$$)³

Question 2.
If the Earth stops rotating about its axis, the value of gat the equator will increase by ……………….. where R is the radius of Earth and co is the angular velocity or rotation.

Question 3.
If the Earth shrinks to half of its radius, its mass remaining the same, the weight of an object on Earth will increase ……………… times.

Question 4.
Let A be the area swept out by the line joining the Earth and Sun during February 2005. The area swept out by the line during a typical week in February 2005 is ………………….

Answer: $$\frac {A}{4}$$

Question 5.
The orbital velocity of the stationary satellite of Earth is nearly ……………..

Answer: 3 km s-1.

Question 6.
The orbit of a planet around the Sun is elliptical with Sun at one of its focii. The point closest to the Sun is called ………….. and the point farthest from the Sun is called ………………

Question 7.
The escape velocity will ……………… if a planet is made bigger keeping its density constant.

Question 8.
The orbital velocity of a satellite in an orbit depends upon the product of …………….. and ……………….

Answer: Acceleration due to gravity at that planet, radius of the planet.

Question 9.
…………….. is defined to be numerically equal to the force of attraction between two bodies each of mass 1kg and separated by a distance of 1 metre.

Answer: Universal gravitational constant (G).

Question 10.
Kepler’s 2nd law of motion which states that the radius vector of a planet from the Sun sweeps out equal area in equal intervals of time is a consequence of ……………….

True/False Type Questions

1. Tell which of the following statement is True/False for the given observation?
An iron and a cork ball of the same size are released from the same height in vacuum. Both of them reach the ground simultaneously. It is due to the following phenomenon:
(а) In vacuum, the acceleration due to gravity is zero.
(b) In vacuum, there is no resistance to the motion of the balls.
(c) Acceleration due to gravity in vacuum is independent of the size of the bodies.
(d) Acceleration due to gravity is independent of the mass of the falling bodies.

(a) False
(b) False
(c) False
(d) True.

2. Tell which of the following statements will be True/False about the observation given here?
If the gravitational attraction of Earth suddenly disappears, then
(a) Both mass as well as the weight will be zero.
(b) Weight of the body will become zero but the mass will remain unchanged.
(c) Weight of the body will remain unchanged but the mass will become zero.
(d) Neither mass nor weight will be zero.

(a) False
(b) True
(c) False
(d) False.

3. Tell which of the following statements are True/False about the variation of the gravitational field strength of Earth?
(a) The gravitational field strength increases when we go below the surface of Earth.
(b) Its magnitude is maximum at the surface of the Earth.
(c) It increases when we go above the surface of the Earth.
(d) “The moon is constantly falling towards Earth.”

(a) False
(b) True
(c) False
(d) True.

4. Tell the True/False statement:
(a) The variation in the speed of the planets in their orbits about the Sun can be explained on the basis of the conservation of angular momentum. .
(b) Moon has no atmosphere because the escape velocity on it is small.
(c) A stationary satellite of a planet orbits at a definite height independent of its own mass.
(d) The time period of a satellite increases as radius of its orbit increases.

(a) True
(b) True
(c) True
(d) True

5. Which of the following is True/False for a stationary satellite of the earth?
(a) It revolves from west to east.
(b) Its time period is 24 hours.
(c) It is stationary in space.
(d) Its angular speed is equal to that of Earth about its own axis.

(a) True
(b) True
(c) False
(d) True

6. Which of the following statement is True/False about the satellite of Earth?
(a) It is weightless.
(b) It is freely falling.body.
(c) It is not accelerated.
(d) It has a constant speed.

(a) True
(b) True
(c) False
(d) True.

7. Which of the following is True/False?
(a) G is a vector quantity.
(b) the weight of a body computed on the Earth is same during 24 hours of the day.
(c) The g will increase if a planet is made bigger keeping its density constant.
(d) The Earth moving around the sun in a circular orbit is acted on by a force and hence work must be done on the Earth by this force.

(a) False
(b) True
(c) True
(d) False.

8. Tell which of the following statements are True/False?
(а) G is not equal to 6.67 × 10-11 Nm² kg-2 on the surface of Earth.
(b) The escape velocity on the surface of Earth is greater than the escape velocity from moon’s surface as moon has no atmosphere but Earth has.
(c) The angular momentum of a satellite going round the Earth remains conserved.
(d) The relation g= $$\frac {GM}{r^2}$$p holds good for all the celestial bodies.

(a) False
(b) False
(c) True
(d) True.

9. Which of the following statements are True/False?
(a) A satellite going round the Earth suffers no acceleration.
(b) A heavier body fails faster than a lighter body under the force of gravity.
(c) The bodies in a uniform gravitational field experience gravitational force proportional to their masses.
(d) g is a scalar quantity.

(a) False
(b) False
(c) True
(d) False.

10. Tell which of the following statements are True/False?
(a) A spaceship entering Earth’s atmosphere is likely to catch fire.
(b) ve > v0 for Earth.
(c) A surface at every point of which the gravitational potential remains same is called equipotential surface.
(d) g at pole is lesser than at the equator.

(a) True
(b) True
(c) True
(d) False.

Match the following columns

 Column I Column II (a) The value of acceleration due to gravity (g) is maximum at (i) the centre of Earth (b) The value of g is minimum at (ii) poles (c) g is zero at (iii) equator

 Column I Column II (a) The value of acceleration due to gravity (g) is maximum at (ii) poles (b) The value of g is minimum at (iii) equator (c) g is zero at (i) the centre of Earth

 Column I Column II (a) The centre of mass is called as the centre of gravity because (i) becomes about 7.41 ms-2 (b) The value of g at a height of 1000 km from Earth’s surface (ii) Torque due to gravity on a body about its centre of mass is zero (c) The moon’s height from Earth is (iii) it does not depend on the nature of the medium between two objects and nature of bodies. (d) The G is called so because (iv) 38 × 10-4 km.

 Column I Column II (a) The centre of mass is called as the centre of gravity because (ii) Torque due to gravity on a body about its centre of mass is zero (b) The value of g at a height of 1000 km from Earth’s surface (i) becomes about 7.41 ms-2 (c) The moon’s height from Earth is (iv) 38 × 10-4 km. (d) The G is called so because (iii) it does not depend on the nature of the medium between two objects and nature of bodies.

 Column I Column II (a) Universal gravitational constant (i) 9.8 ms-2 (b) Acceleration due to gravity on the surface of Earth (ii) 1.63 ms-2 (c) Acceleration due to  gravity on moon (iii) 6.67 × 10-11 Nm²kg-2

 Column I Column II (a) Universal gravitational constant (iii) 6.67 × 10-11 Nm²kg-2 (b) Acceleration due to gravity on the surface of Earth (i) 9.8 ms-2 (c) Acceleration due to  gravity on moon (ii) 1.63 ms-2

 Column I Column II (a) it is measured by studying the motion (acceleration) produced by the applied force. (i) acceleration due to gravity (b) It is measured by studying the gravitationtel pull on it (ii) inertial mass (c) It varies due to the shape of Earth (iii) Gravitational mass

 Column I Column II (a) it is measured by studying the motion (acceleration) produced by the applied force. (ii) inertial mass (b) It is measured by studying the gravitationtel pull on it (iii) Gravitational mass (c) It varies due to the shape of Earth (i) acceleration due to gravity

 Column I Column II (а) The angle made by the line joining the point on earth’s surface to the centre of Earth with the equitorial plane (i) 90° (b) Value of λ at pole (ii) zero (0°) (c) Value of λ at equator (iii) latitude at a point

 Column I Column II (а) The angle made by the line joining the point on earth’s surface to the centre of Earth with the equitorial plane (iii) latitude at a point (b) Value of λ at pole (i) 90° (c) Value of λ at equator (ii) zero (0°)

 Column I Column II (a) Difference between the value of g at pole and equator of Earth of radius 6.37 × 106 m is (i) equal (b) Torque due to gravity on a body about its C.M. (ii) 3.37 × 10-2 ms-2 (c) Earth’s attraction for 2kg of iron and attraction of 2kg of iron on Earth (iii) zero

 Column I Column II (a) Difference between the value of g at pole and equator of Earth of radius 6.37 × 106 m is (ii) 3.37 × 10-2 ms-2 (b) Torque due to gravity on a body about its C.M. (iii) zero (c) Earth’s attraction for 2kg of iron and attraction of 2kg of iron on Earth (i) equal

 Column I Column II (a) Essential property of matter (i) rotation of Earth (b) The value of ‘g’ does not change due to rotational motion of Earth (ii) mass (c) The acceleration due to gravity decreases due to (iii) at poles

 Column I Column II (a) Essential property of matter (ii) mass (b) The value of ‘g’ does not change due to rotational motion of Earth (iii) at poles (c) The acceleration due to gravity decreases due to (i) rotation of Earth

 Column I Column II (a) Orbital velocity of a  satellite near Earth’s surface (i) 2.38 kms-1 (b) Escape velocity on Earth’s surface (ii) 7.92 kms-1 (c) Escape velocity at moon (iii) 11.2 kms-1

 Column I Column II (a) Orbital velocity of a  satellite near Earth’s surface (ii) 7.92 kms-1 (b) Escape velocity on Earth’s surface (iii) 11.2 kms-1 (c) Escape velocity at moon (i) 2.38 kms-1

 Column I Column II (a) It can never have a positive value (i) Escape velocity (b) It does not depend upon the mass of the object to be projected (ii) Gravitational potential (c) Potential energy of a galaxy is negative as (iii) The forces between different galaxies are attractive in nature