NCERT Class 11 Physics Gravitation

NCERT Class 11 Physics Gravitation - NCERT Solutions prepared for CBSE students by the best teachers in Delhi. Students should free download the NCERT solutions and get better marks in exams. For more study material for physics click here - class 11 physics chapter 1 physical world notes

Class XI Physics

Ch. 8: Gravitation

NCERT Solutions

Page 201

Question 8.1:

Answer the following:

(a) You can shield a charge from electrical forces by putting it inside a hollow conductor. Can you shield a body from the gravitational influence of nearby matter by putting it inside a hollow sphere or by some other means?

(b) An astronaut inside a small space ship orbiting around the earth cannot detect gravity. If the space station orbiting around the earth has a large size, can he hope to detect gravity?

(c) If you compare the gravitational force on the earth due to the sun to that due to the moon, you would find that the Sun’s pull is greater than the moon’s pull. (You can check this yourself using the data available in the succeeding exercises). However, the tidal effect of the moon’s pull is greater than the tidal effect of sun. Why?

  ANS:  (a) No (b) Yes

   (a) Gravitational influence of matter on nearby objects cannot be screened by any means. This is because gravitational force unlike electrical forces is independent of the nature of the material medium. Also, it is independent of the status of other objects.

   (b) If the size of the space station is large enough, then the astronaut will detect the change in Earth’s gravity (g).

   (c) Tidal effect depends inversely upon the cube of the distance while, gravitational

force depends inversely on the square of the distance. Since the distance between the Moon and the Earth is smaller than the distance between the Sun and the Earth, the tidal effect of the Moon’s pull is greater than the tidal effect of the Sun’s pull.

Question 8.2:

Choose the correct alternative:

(a) Acceleration due to gravity increases/decreases with increasing altitude.

(b) Acceleration due to gravity increases/decreases with increasing depth. (assume the earth to be a sphere of uniform density).

(c) Acceleration due to gravity is independent of mass of the earth/mass of the body.

(d) The formula –G Mm(1/r2– 1/r1) is more/less accurate than the formula mg(r2–

r1) for the difference of potential energy between two points r2and r1distance away

from the centre of the earth.

ANS:

(a) Decreases

(b) Decreases

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