NCERT Book Class 9 Science Gravitation Questions

GRAVITATION

1. Two objects of different masses falling freely near the surface of moon would

(a) have same velocities at any instant

(b) have different accelerations

(c) experience forces of same magnitude

(d) undergo a change in their inertia

2. The value of acceleration due to gravity

(a) is same on equator and poles

(b) is least on poles

(c) is least on equator

(d) increases from pole to equator

3. The gravitational force between two objects is F. If masses of both objects are halved without changing distance between them, then the gravitational force would become

(a) F/4    (b) F/2    (c) F     (d) 2 F

4. A boy is whirling a stone tied with a string in an horizontal circular path. If the string breaks, the stone

(a) will continue to move in the circular path

(b) will move along a straight line towards the centre of the circular path

(c) will move along a straight line tangential to the circular path

(d) will move along a straight line perpendicular to the circular path away from the boy

5. Law of gravitation gives the gravitational force between

(a) the earth and a point mass only

(b) the earth and Sun only

(c) any two bodies having some mass

(d) two charged bodies only

6. What is the source of centripetal force that a planet requires to revolve around the Sun? On what factors does that force depend?

7. On the earth, a stone is thrown from a height in a direction parallel to the earth’s surface while another stone is simultaneously dropped from the same height. Which stone would reach the ground first and why?

8. Suppose gravity of earth suddenly becomes zero, then in which direction will the moon begin to move if no other celestial body affects it?

9. Identical packets are dropped from two aeroplanes, one above the equator and the other above the north pole, both at height h. Assuming all conditions are identical, will those packets take same time to reach the surface of earth. Justify your answer.

10. The weight of any person on the moon is about 1/6 times that on the mass, which can be lifted by the same force applied by the person on themoon?

11. Calculate the average density of the earth in terms of g, G and R.

12. The earth is acted upon by gravitation of Sun, even though it does not fallinto the Sun. Why?

Please refer to attached file for NCERT Class 9 Science Gravitation Questions