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This mock test of MCQ : Gravitation - 1 for Class 9 helps you for every Class 9 entrance exam.
This contains 10 Multiple Choice Questions for Class 9 MCQ : Gravitation - 1 (mcq) to study with solutions a complete question bank.
The solved questions answers in this MCQ : Gravitation - 1 quiz give you a good mix of easy questions and tough questions. Class 9
students definitely take this MCQ : Gravitation - 1 exercise for a better result in the exam. You can find other MCQ : Gravitation - 1 extra questions,
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QUESTION: 1

Variation of g with distance r from the centre of earth with (r > R_{e}) is best given by:

Solution:

With depth, g_{1} = g {1− (d)/R}

As depth d goes on increasing, g1 goes on decreasing, it remains maximum at the surface of Earth. The above equation is in the form of a straight line.

With height, g_{2} = g (1 − 2h/R) = g − 2gh/R

g_{2} ∝ 1/R (Hyperbola)

Acceleration due to gravity goes on decreasing as the h above Earth surface increases.

QUESTION: 2

The SI unit of G is:

Solution:

In SI units, G has the value 6.67 × 10^{-11} N kg^{-2} m^{2}.

QUESTION: 3

Four planets A, B, C, and D made up of the same material have a radius of r/2, r, 2r, and 4r respectively. The order of the planets in increasing order of the acceleration due to gravity (on their surface) is:

Solution:

If radius is half then the gravity will be double and single is r then gravity will be 9.8 m/s2. if radius is 2r then the gravity will decrease and if radius is 4r then the gravity will also decrease because the gravity is inversely proportional to the square of radius.

Hence the correct answer would be, r/2>r>2r>4r i.e option D.

QUESTION: 4

The tidal waves in the sea are primarily due to______.

Solution:

- Moon is the
**closest heavenly body**to the Earth. The sun is approximately**400 times**farther than the Moon. Hence, its Gravitational pull is weaker than the Moon. - So, the tides are mainly caused by the
**Gravitational interaction between Moon & Earth.**

QUESTION: 5

The wrong option about gravitational force among the following is______.

Solution:

- An action-reaction pair of forces are always equal and opposite, but two forces that are equal in magnitude and opposite in direction are NOT always an action-reaction pair!
- On the other hand, the reaction force to the normal force pushing up on the book is the force of the book pushing down on the table.

QUESTION: 6

An object weighs 10 N when measured on the surface of the earth. What should be its weight on the moon?

Solution:

Acceleration due to gravity at the moon is **(1/6) ^{th }times** of that at the earth.

So, weight on moon, W

QUESTION: 7

A 60 kg man weighs W kg on the moon. W is:

Solution:

The moon's gravity is one-sixth that of Earth, so the weight of a 60kg human on the moon will be **10kg**.

QUESTION: 8

The weight of an object______.

Solution:

- The weight of an object is the force with which it is attracted towards the earth. The SI unit of weight is the same as that of force, that is,
**newton (N).** - The weight is a force acting vertically downwards; it has both
**magnitude and direction.** **w = m*g**

QUESTION: 9

Acceleration due to gravity on the surface of the moon is 1/6th of its value on the surface of the earth as they have different______.

Solution:

QUESTION: 10

The force of gravitation between two bodies varies with r as:

Solution:

By Newton's universal law of gravitation, **F = Gm _{1}m_{2} / r^{2}**. Thus, F is inversely proportional to r

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