NCERT Class 11 Physics Solutions: Chapter 8 – Gravitation-Part 2

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Question 8.3:

Suppose there existed a planet that went around the sun twice as fast as the earth. What would be its orbital size as compared to that of the earth?

Answer:

Lesser by a factor of times

Explanation:

The distance beteween sun and earth 63 times showing in figu …

Figure Shown the Distance Beteween Sun and Earth

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Time taken by the Earth to complete one revolution around the Sun,

Orbital radius of the Earth in its orbit,

Time taken by the planet to complete one revolution around the Sun,

Orbital radius of the planet

From Kepler’s third law of planetary motion, we can write:

Hence, the orbital radius of the planet will be smaller than that of the Earth.

Question 8.4:

, one of the satellites of Jupiter, has an orbital period of days and the radius of the orbit is . Show that the mass of Jupiter is about one-thousandth that of the sun.

Answer:

Orbital period of

Orbital radius of

Satellite is revolving around the Jupiter

The mass of Jupiter is about one-thousandth that of the Sun …

Mass of Jupiter is About One-Thousandth That of the Sun

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Mass of the latter is given by the relation:

Where,

Mass of Jupiter

Universal gravitational constant

Orbital period of the earth,

Orbital radius of the Earth,

Mass of Sun is given as:

Hence, it can be inferred that the mass of Jupiter is about one-thousandth that of the Sun.

Question 8.5:

Let us assume that our galaxy consists of stars each of one solar mass. How long will a star at a distance of from the galactic centre take to complete one revolution? Take the diameter of the Milky Way to be

Answer:

Mass of our galaxy Milky Way, solar mass

Solar mass Mass of Sun

Mass of our galaxy,

Diameter of Milky Way,

Radius of Milky Way,

star revolves around the galactic centre of the Milky Way, i …

Galactic Centre of the Milky Way, Its Time Period

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Since a star revolves around the galactic centre of the Milky Way, its time period is given by the relation: