Comprehension

From a vantage point in space, an observer could see that the Earth is engaged in a variety of motions. First, there is its rotation on its own axis, causing the alternation of day and night. This rotation, however, is not altogether steady. Primarily because of the moon’s gravitational action, the Earth‘s axis wobbles like that of an ill-spun top. In this motion, called ‘precession’, the North and South Poles each traces out the base of a cone in space, completing a circle every 25,800 years. In addition, as the Sun and the Moon change their positions with respect to the Earth, their changing gravitational effects result in a slight ‘nodding’ of the earth’s axis, called ‘mutation’, which is superimposed on precession. The Earth completes one of these ‘nods’ every 18.6 years.
The earth also, of course, revolves round the Sun, in a 6-million mile journey that takes 365.25 days. The shape of this orbit is an ellipse, but it is not the center of the Earth that follows the elliptical path. Earth and Moon behave like an asymmetrical dumb-bell, and it is the center of mass of this dumb-bell that traces the ellipse around the sun. The center of the Earth-Moon mass lies about 3000 miles away from the center of the Earth, and the Earth thus moves in an S-curve that crosses and recrosses its orbital path. Then too, the Earth accompanies the sun in the sun’s movements: first, through its local star cloud, and second, in a great sweep around the hub of its galaxy, the Milky Way that takes 200 million years to complete.

Question: 1

The passage is most likely directed towards an audience of

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Simple language and everyday analogies suggest a passage is aimed at non-experts in the subject.
Updated On: Jul 24, 2025
  • geologists
  • astronauts
  • meteorologists interested in weather prediction
  • person with little technical knowledge of astronomy
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The Correct Option is D

Solution and Explanation

Step 1: The passage explains Earth’s motions (rotation, precession, nutation, orbit) using simple analogies (e.g., a spinning top, dumb-bell) and non-technical language.
Step 2: This suggests it targets readers without specialized astronomical knowledge.
Step 3: Option D (persons with little technical knowledge of astronomy) matches this approach.
Step 4: Option A (geologists) is incorrect as the passage focuses on astronomy, not geology.
Step 5: Option B (astronauts) implies technical expertise, which the passage avoids.
Step 6: Option C (meteorologists) is irrelevant as weather prediction is not discussed.
Verification: The passage’s simple explanations indicate it’s for a general audience, supporting option D.
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Question: 2

Which of the following best describes the main subject of the passage?

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The main subject is often introduced in the opening sentence and elaborated throughout the passage.
Updated On: Jul 24, 2025
  • The various types of the Earth’s motions
  • Past changes in the Earth’s position
  • The moon’s gravitational effect on the Earth
  • Oddities of the Earth’s rotation of its axis
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The Correct Option is A

Solution and Explanation

Step 1: The passage begins by stating that an observer could see the Earth engaged in various motions, then describes rotation, precession, nutation, and orbital motion.
Step 2: The main focus is on these different types of motions, not just one aspect.
Step 3: Option A (various types of Earth’s motions) captures this comprehensive focus.
Step 4: Option B (past changes) is incorrect as the passage discusses current motions, not historical changes.
Step 5: Option C (moon’s effect) is too narrow, covering only part of the discussion.
Step 6: Option D (rotation oddities) focuses only on one motion, not the variety.
Verification: Option A aligns with the passage’s broad coverage of Earth’s motions.
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Question: 3

The passage indicates that a single cycle of which of the following motions is completed in the shortest period of time?

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Compare time periods directly from the passage to identify the shortest cycle in time-based questions.
Updated On: Jul 24, 2025
  • Nutation
  • Precession
  • The Earth’s rotation on its axis
  • The movement around the hub of the Milky Way
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The Correct Option is C

Solution and Explanation

Step 1: The passage lists time periods for Earth’s motions: rotation on its axis (day and night, 24 hours), precession (25,800 years), nutation (18.6 years), and Milky Way orbit (200 million years).
Step 2: Comparing these, rotation on the axis (24 hours) is the shortest cycle.
Step 3: Option C (Earth’s rotation on its axis) matches this.
Step 4: Option A (nutation, 18.6 years) is much longer.
Step 5: Option B (precession, 25,800 years) is even longer.
Step 6: Option D (Milky Way orbit, 200 million years) is the longest.
Verification: Rotation’s 24-hour cycle is clearly the shortest period mentioned.
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Question: 4

Which of the following techniques does the author use in order to make the descriptions of motion clear? I. Comparison with familiar objects.
II. Reference of geometric forms.
III. Allusions to the works of other authors.

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In questions about literary techniques or explanations in scientific passages, always look for comparisons to everyday objects and references to shapes or structures. These techniques help simplify complex ideas and make them more relatable to the reader.
Updated On: Jul 24, 2025
  • I only
  • II only
  • I and II only
  • II and III only
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The Correct Option is C

Solution and Explanation

To determine which techniques the author uses to explain the motion of the Earth, we need to carefully analyze the passage for the presence of each described technique. Let's break it down step by step:
1. Comparison with familiar objects (I):
- The author compares the Earth's wobble due to precession to an **"ill-spin top"**. This comparison uses a familiar object, the spinning top, which most readers can visualize, thereby helping to clarify the concept of the Earth's wobble.
- This comparison allows the reader to imagine the Earth's motion more clearly because they can relate to the spinning top, which is a simple and commonly known object.
Since this comparison is explicitly mentioned in the passage, technique I is used.
2. Reference to geometric forms (II):
- The passage mentions the "ellipse" that the Earth follows in its journey around the Sun. The description explicitly refers to the "geometric shape" of the Earth's orbit, calling it an "ellipse". It also talks about the Earth's axis wobbling in a cone, which is a "geometrical shape".
- Additionally, the shape of the Earth's path is explained using a "mathematical/geometry-based" perspective, giving the reader a clear visualization of the Earth's movement.
As this reference to geometric forms is clearly present, technique II is also used.
3. Allusions to the works of other authors (III): - The passage does not reference or allude to any works of other authors. There is no mention of any external figures, ideas, or theories from other sources. The description is entirely based on scientific facts and visualizations about the Earth's motion.
Therefore, technique III is not used.
Conclusion:
- The passage uses comparison with familiar objects (like the ill-spin top) and reference to geometric forms (like the ellipse and cone) to explain the Earth's motion.
- Since technique III is not mentioned, the correct answer is (c) I and II only.
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