# CBSE Worksheet for chapter-6 Gravitation class 9

## Find CBSE Worksheet for chapter-6 Gravitation class 9

CLASS-9

BOARD: CBSE

Physics Worksheet - 6

TOPIC: Gravitation

For other CBSE Worksheet for class 9 Science check out main page of Physics Wallah.

SUMMARY

• Introduction

• Newton’s laws of Gravitation - Universal law of Gravitation, Mathematical derivation

• Newton’s third law of motion and Gravitation, Acceleration due to gravity

• Mass of Earth and Mean density of Earth, Factors affecting the value of ‘g’

• Mass and Weight, Weightlessness, Keplers’s Laws of Planetary motion

SECTION I – OBJECTIVE

1. When an apple falls from a tree:

(A) Only earth attracts the apple (B) Only apple attracts the earth

(C) Both the earth and an apple attract each other (D) None of these

2. When the medium between two bodies changes, force of gravitation between them:

(A) Will increase.

(B) Will decrease

(C) Will change according to environment

(D) Remains same

3. The value of G in year 1900 was 6.673x10-11 Nm2/kg2. The value of G in year 2007 will be:

(A) 6.673x10-9 Nm2/kg2

(B) 6.673x10-10 Nm2 kg2

(C) 6.673x10-2 Nm2/kg2

(D) 6.673x10-11 Nm2/kg2

4. Choose the correct statement:

(A) All bodies repel each other in the 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

5. If a initially the distance between two bodies is r and their masses are M1 and M2 then the force of gravitation be F. If this distance is increased to two times then force would become:

(A) F/2

(B) F/4

(C) 2F

(D) 4F

6. Force between two masses of 1 kg each, are separated by a distance 1 metre will be:

(A) 6.67x10-11 N

(B) 9.8 N

(C) 6.67x10-8 N

(D) 6.67x10-12 N

7. If a planet existed whose mass and radius were both half of the earth, the acceleration due to gravity at the surface would be:

(A)19.6 m/s2

(B) 9.8 m/s2

(C) 4.9 m/s2

(D) 2.45 m/s2

8. The ratio of the value of g on the surface of moon to that on the earth’s surface is:

(A) 6

(B) √6

(C) 1/6

(D)1/√6

9. A particle is taken to a height R above the earth’s surface, where R is the radius of the earth.

The acceleration due to gravity there is:

(A) 2.45 m/s2

(B) 4.9 m/s2

(C) 9.8 m/s2

(D) 19.6 m/s2

10. The weight of a body is 120 N on the earth. If it is taken to the moon, its weight will be about:

(A) 120 N

(B) 60 N

(C) 20 N

(D) 720 N

SECTION II - SUBJECTIVE

1. State Kepler’s laws of planetary motion.

2. Explain weightlessness.

3. Differentiate between following.

(a) Mass and Weight

(b) Acceleration due to gravity ’g’ and Universal gravitational constant ‘G’

4. A ball is thrown vertically upwards with a velocity ‘u’. Calculate the speed with which it falls to the earth again.

5. State factors affecting the value of ‘g’.

6. State the universal law of gravitation.

7. Name the scientist who gave the universal law of gravitation.

8. Two persons having mass 50 kg each are standing such that their centre of gravity are 1 m apart.

Calculate the mutual force of gravitation they exert on each other and also calculate the force of gravity due to earth on each.

(Take G = 6.67x10-11 Nm2 / kg2, mass of earth M = 6x1024 kg, radius of earth R = 6.4x106 m.)

### Solutions: to worksheet-6 Gravitation class 9  With Solutions

#### Objective Problems:

 1.(C) 2.(D) 3.(D) 4.(D) 5.(B) 6.(A) 7.(A) 8.(C) 9.(A) 10.(C)

### Subjective Problems :

4. The body falls back to the earth with the same speed with which it was thrown vertically upwards.

8. F= 1.67x10-7 N.

F’= 0.48x103 N.

F’ is much greater than F so the persons will not move towards each other but each of them moves towards the earth.