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Test: Gravitation - 2

25 Questions MCQ Test NCERT Textbooks (Class 6 to Class 12) | Test: Gravitation - 2

Description

Attempt Test: Gravitation - 2 | 25 questions in 25 minutes | Mock test for UPSC preparation | Free important questions MCQ to study NCERT Textbooks (Class 6 to Class 12) for UPSC Exam | Download free PDF with solutions

QUESTION: 1

If a rock is brought from the surface of the moon

A.
Its mass will change
B.
Its weight will change but not mass
C.
Both mass and weight will change
D.
Its mass and weight both will remain same

Solution:

B is the correct option.If a rock is brought from the surface of the moon to the earth, its weight will change but not its mass. Mass is an invariant physical quantity whereas weight of a body (w = mg) is variable as the value of acceleration due to gravity (g) changes

QUESTION: 2

A body is weighed at the poles and then at the equator. The weight

A.
At the equator will be greater than at the poles
B.
At the poles will be greater than at the equator
C.
At the poles will be equal to the weight at the equator
D.
Depends upon the object

Solution:

A body weighs more at the poles than at the equator, because the earth is not a perfect square, but it is flattened at the poles. The distance between the equator and the center of the earth is less than at the poles; therefore the force of gravitation is more at the poles than at the equator; and so it weighs more at the poles than equator.
Hence, the weight of a body at the poles will be greater than at the equator.

QUESTION: 3

Consider a satellite going round the earth in a circular orbit. Which of the following statements is wrong ?

A.
It is a freely falling body
B.
It is moving with constant speed
C.
It suffers no acceleration
D.
Its angular momentum remains constant

Solution:

Centripetal acceleration works on it.

QUESTION: 4

A missile is launched with a velocity less than the escape velocity. The sum of its kinetic and potential energy is

A.
Positive
B.
Negative
C.
Zero
D.
May be positive or negative depending upon its initial velocity

Solution:

Kinetic energy would be obvious = 0.5mv^2

and the potential Energy would be= -Gm/r^2

Now total energy = 0.5mv^2 – Gm/r^2 hence would be negative as r approaches infinity.

QUESTION: 5

SI unit of g is

A.
m²/s
B.
s/m²
C.
m/s²
D.
m/s

Solution:

QUESTION: 6

SI unit of G is

A.
N²–m²/kg
B.
N–m²/kg
C.
N–m/kg
D.
N -m²/kg²

Solution:

In SI units, G has the value 6.67 × 10-11 Newtons kg-2 m2. The direction of the force is in a straight line between the two bodies and is attractive. Thus, an apple falls from a tree because it feels the gravitational force of the Earth and is therefore subject to “gravity”.

QUESTION: 7

Choose the correct statement of the following:

A.
All bodies repel each other in this universe
B.
Our earth does not behave like a magnet
C.
Acceleration due to gravity is 8.9 m/s²
D.
All bodies fall at the same rate in vacuum

Solution:

So all objects, regardless of size or shape or weight, free fall with the same acceleration. In a vacuum, a beach ball falls at the same rate as an airliner. ... The remarkable observation that all free falling objects fall with the same acceleration was first proposed by Galileo Galilei nearly 400 years ago.

QUESTION: 8

Maximum weight of a body is

A.
At the centre of the earth
B.
Inside the earth
C.
On the surface of the earth
D.
Above the surface of earth

Solution:

At the center gravity is 0 ,gravity decreases as we go down into the earth ,also it decreases as we go above the surface of earth.
So weight w = mg is maximum on the surface because at surface the value of g is maximum.

QUESTION: 9

If the distance between two masses be doubled, then the force between them will become

A.
1/4 times
B.
4 times
C.
1/2 times
D.
2 times

Solution:

The Gravitational force between two objects is inversely proportional to the square of distance between them.
So, if the distance between two objects is doubled, then the gravitational force becomes 1 / 2x2.
That is ¼.

QUESTION: 10

A body falls freely towards the earth with

A.
Uniform speed
B.
Uniform velocity
C.
Uniform acceleration
D.
None of these

Solution:

The correct answer is C as body falls freely towards the earth with uniform acceleration (g).

QUESTION: 11

If the mass of a body is M on the surface of the earth, then its mass on the surface of the moon will be

A.
M/6
B.
M
C.
M + 6
D.
Zero

Solution:

The correct option is B.
Mass of the body is universally the same. It is not affected by acceleration due to gravity and thus is the same everywhere. Hence, mass of body will be same i.e. M at both earth surface & moon surface.

QUESTION: 12

Weight

A.
Is a vector quantity
B.
Of a body in interplanetary space is maximum
C.
Increases when the bodies go up
D.
None of these

Solution:

QUESTION: 13

The value of g near the earth's surface is

A.
8.9 m/s²
B.
8.9 m/s
C.
9.8 m/s²
D.
9.8 m/s

Solution:

QUESTION: 14

A geostationary satellite

A.
Moves faster than the near earth satellite
B.
Has a time period less that of a near earth satellite
C.
Revolves about the polar axis
D.
Is stationary in space

Solution:

A geostationary satellite revolves around the earth with the same angular velocity and in the same sense as done by the earth about its own axis, i.e. west-east direction. A polar satellite revolves around the earth's pole in north-south direction.

QUESTION: 15

The force of gravitation between two bodies depend upon

A.
Their separation
B.
Gravitational constant
C.
Product of their masses
D.
All of these

Solution:

QUESTION: 16

When an object is thrown up, the force of gravity

A.
Acts in the direction of the motion
B.
Acts in the opposite direction of the motion
C.
Remains constant as the body moves up
D.
Increases as the body moves up

Solution:

QUESTION: 17

The force of gravitation exists

A.
Everywhere in the universe
B.
At the surface of the earth only
C.
Inside the earth only
D.
At the surface of the moon only

Solution:

The correct answer is A as The force of gravitation exists Everywhere in the universe

QUESTION: 18

1 kg wt is equal to

A.
9.8 N
B.
980 N
C.
98 N
D.
None of these

Solution: 1 kg-wt and express it in newton. 1 kilogram weight is that gravitational force which acts on a body of mass 1 kg. This means that the weight of 1 kgmass is 9.8 N.
Hence the answer is option (a)

QUESTION: 19

Mass of oil is 11040 kg and volume is 12 m³, its density would be

A.
92 kg m^-3
B.
920 kg m^-3
C.
9.2 kg m^-3
D.
1.08 × 10^-3

Solution:

Density,
ρ = M / V = 11040 / 12
= 920 kg/m³

QUESTION: 20

The value of G does not depend on

A.
Nature of the interacting bodies
B.
Size of the interacting bodies
C.
Mass of the interacting bodies
D.
All of these

Solution:

QUESTION: 21

The mass of the Jupiter is 1.9 × 10²⁷ kg and that of the sun is 1.99 × 10³⁸kg. 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

Solution:

F = GMm / r²
= 6.67×10-¹¹ × (1.99×10³⁰) × (1.9×10²⁷) / (7.8×10¹¹)²
= 4.14×10²³ N
Now let its speed of jupiter be v, then
F = mv² / R
⇒ v =√(FR / m)
=√{(7.8×10¹¹)×(4.10×10²³) / (1.9×10²⁷)}
= 1.304×10⁴ m/sec

QUESTION: 22

The acceleration due to gravity

A.
has the same value everywhere in space

has the same value everywhere on the earth
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

Solution:

QUESTION: 23

SI unit of weight is

A.
kg wt
B.
N
C.
g wt
D.
none of these

Solution:

Weight is nothing but the force of attraction exerted by the earth on a body.
Now since the SI unit of force is Newton and the weight is also a force, this means that the SI or weight is Newton as well.

QUESTION: 24

Gravitational force which acts on 1 kg is