Concept explainers
(a)
The distance between the center of mass of the Earth-Moon system and the center of Earth using the expression,
(a)
Answer to Problem 21Q
Solution:
Explanation of Solution
Introduction:
The distance between the center of mass of a two worlds system and the center of world 1
Explanation:
Recall the expression for the distance between the center of mass of the Earth-Moon system and the center of Earth, considering Earth as world 1 and the Moon as world 2, and their respective centers being an average distance apart from each other as:
Substitute
Conclusion:
Hence, the distance between the center of mass of the Earth-Moon system and the center of Earth is
(b)
Whether the center of mass of the Earth-Moon system is beneath the earth’s surface and if yes, then also determine the depth of it from the surface of Earth.
(b)
Answer to Problem 21Q
Solution:
The center of mass of the Earth-Moon system is within the Earth, at a distance of about
Explanation of Solution
Introduction:
The center of mass of the Earth-Moon system lies on the imaginary line joining the centers of both the worlds, and since the mass of Earth is much more than that of the Moon, the center of mass will lie closer to Earth’s center and beneath its surface.
Therefore, the distance between the center of mass of the system and the Earth’s surface is:
Here,
Explanation:
Refer to the sub-part (a) of the problem and compare the value of the distance of the center of mass of the Earth-Moon system with the standard value of Earth’s radius. It is observed that the radius of Earth is much larger than the distance of the center of mass of the system. This can be represented as,
Hence, the center of mass of the system will lie within the Earth, below its surface.
Now, recall the expression for the distance between the center of mass of the system and Earth’s surface as:
Substitute
Conclusion:
Hence, the center of mass of the Earth-Moon system lies beneath the surface of Earth at a distance of about
(c)
The distance between the center of the Sun and the center of mass of the Sun-Earth system, if the first world is the Sun and the second world is Earth using the expression,
(c)
Answer to Problem 21Q
Solution:
Distance of the center of mass of the Sun-Earth system is around
Explanation of Solution
Introduction:
The distance between the center of mass of a two worlds system and the center of world 1
Explanation:
Recall the expression for the distance between the center of mass of the Sun-Earth system and the center of the Sun, considering the Sun as world 1 and Earth as world 2:
Substitute
Compare the value calculated above with the standard value of the radius of the Sun, which is
It is observed that the value of the distance between the center of mass of the system and the center of the Sun is almost
Therefore, it can be safely assumed that Earth revolves around the center of the Sun.
Conclusion:
Hence, the distance between the center of mass of the Sun-Earth system and the center of the Sun is around
Therefore, it is safe to assume that Earth revolves around the Sun’s center.
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Chapter 10 Solutions
Universe
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