The Earth And The Solar System (continued 2)
Overview
The Sun holds more than 99 percent of the mass of the Solar System, and that vast mass is what keeps eight planets, countless asteroids and long-tailed comets sweeping around it. The same gravity that gives you weight on Earth reaches across hundreds of millions of kilometres to hold whole worlds in orbit.
In this topic you will learn what controls a planet's gravitational field strength, calculate how long light takes to cross the Solar System, and see why the Sun's gravity keeps the planets in orbit. You will also explore how orbital speed changes with distance from the Sun and use conservation of energy to explain why a comet races when it is close to the Sun.
Objectives
- Know that the strength of the gravitational field (a) at the surface of a planet depends on the mass of the planet (b) around a planet decreases as the distance from the planet increases
- Calculate the time it takes light to travel a significant distance such as between objects in the Solar System
- Know that the Sun contains most of the mass of the Solar System and this explains why the planets orbit the Sun
- Know that the force that keeps an object in orbit around the Sun is the gravitational attraction of the Sun
- [Supplement] Know that the strength of the Sun’s gravitational field decreases and that the orbital speeds of the planets decrease as the distance from the Sun increases
- [Supplement] Know that an object in an elliptical orbit travels faster when closer to the Sun and explain this using the conservation of energy
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Lesson Evaluation
Congratulations on completing the lesson on The Earth And The Solar System (continued 2). Now that you've explored the key concepts and ideas, it's 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.
- The gravitational field strength at the surface of a planet depends on the planet's: A. colour B. mass C. number of moons D. temperature Answer: B
- Light takes about how long to travel from the Sun to the Earth? A. 8 seconds B. 8 minutes C. 8 hours D. 8 days Answer: B
- The planets orbit the Sun because of: A. magnetic attraction B. the Sun's gravitational attraction C. the solar wind D. air resistance Answer: B
- As distance from the Sun increases, the orbital speed of a planet: A. increases B. decreases C. stays the same D. becomes zero Answer: B
- A comet in an elliptical orbit moves fastest when it is: A. farthest from the Sun B. closest to the Sun C. at constant distance D. outside the Solar System Answer: B
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Recommended Books
Further learning from open sources
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Textbook section
Newton’s Universal Law of Gravitation
What do aching feet, a falling apple, and the orbit of the Moon have in common? Each is caused by the gravitational force. Our feet are strained by supporting our weight—the force of Earth’s gravity on us. An apple falls from a tree because of the same force acting a few meters above Earth’s surface
"College Physics: Newton’s Universal Law of Gravitation" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/6-5-newtons-universal-law-of-gravitation. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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Textbook section
Satellites and Kepler’s Laws: An Argument for Simplicity
Examples of gravitational orbits abound. Hundreds of artificial satellites orbit Earth together with thousands of pieces of debris. The Moon’s orbit about Earth has intrigued humans from time immemorial. The orbits of planets, asteroids, meteors, and comets about the Sun are no less interesting. If
"College Physics: Satellites and Kepler’s Laws: An Argument for Simplicity" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/6-6-satellites-and-keplers-laws-an-argument-for-simplicity. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
Published by other organisations under open licences, credited as they ask. Links open their websites.
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