Physics (9-1) - 0972 CIE

The Earth And The Solar System

Overview

Day and night, the march of the seasons, the changing face of the Moon: the great rhythms of the sky all come from a few simple motions. The Earth spins, the Earth orbits the Sun, and the Moon orbits the Earth, and from those three facts the whole pattern follows.

In this lesson you will use the Earth's tilted spin to explain day and night and the apparent motion of the Sun, its yearly orbit to explain the seasons, the Moon's monthly orbit to explain its phases, and the orbital-speed equation to calculate how fast a body moves around its orbit.

Objectives

  1. Know that the Earth is a planet that rotates on its axis, which is tilted, once in approximately 24 hours, and use this to explain observations of the apparent daily motion of the Sun and the periodic cycle of day and night
  2. Know that the Earth orbits the Sun once in approximately 365 days and use this to explain the periodic nature of the seasons
  3. Know that it takes approximately one month for the Moon to orbit the Earth and use this to explain the periodic nature of the Moon’s cycle of phases
  4. [Supplement] Define average orbital speed from the equation 2π r v = T where r is the average radius of the orbit and T is the orbital period; recall and use this equation

Lesson Note

Astronomy begins at home. Before you can understand stars and galaxies, you need to explain the everyday sky: why the Sun appears to cross it, why summer differs from winter, and why the Moon waxes and wanes. All of it comes from rotation and orbits, and the same orbital-speed idea applies to planets, moons and satellites alike.

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Lesson Evaluation

Congratulations on completing the lesson on The Earth And The Solar System. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. Day and night are caused by the Earth: A. orbiting the Sun B. rotating on its axis C. tilting its axis D. moving towards the Sun Answer: B
  2. The seasons are mainly caused by: A. the Earth's distance from the Sun changing B. the tilt of the Earth's axis C. the Moon's orbit D. the Sun moving Answer: B
  3. The Moon takes approximately how long to orbit the Earth? A. one day B. one week C. one month D. one year Answer: C
  4. A body orbits at radius r with period T. Its orbital speed is: A. r/T B. 2 pi r / T C. pi r^2 / T D. T / r Answer: B
  5. A satellite orbits at r = 7.0 x 10^6 m with T = 6000 s. Its speed is about: A. 1200 m/s B. 7300 m/s C. 44000 m/s D. 73000 m/s Answer: B

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Full lesson notes with diagrams
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Available on the Green Bridge App

Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.

Full lesson notes with diagrams
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Study offline, anytime, anywhere
Available on Android, Windows, macOS, and Linux

Practice Mock Questions

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