Motion In The Universe
Overview
Look up on a clear night and you are staring into the same universe that ancient sailors used to navigate and that modern telescopes are still mapping. From our nearest neighbour, the Moon, to galaxies billions of light-years away, the universe is organised into a hierarchy of structures held together by gravity.
In this lesson you will learn how planets, moons, comets and asteroids move through the solar system, why some orbits are circular and others are stretched, and how to calculate the speed of any orbiting body. These ideas appear regularly on Edexcel Papers 1 and 2, often as calculation or comparison questions.
Objectives
- Know that the universe is a large collection of billions of galaxies, a galaxy is a large collection of billions of stars, and our solar system is in the Milky Way galaxy
- Understand why gravitational field strength, g, varies and know that it is different on other planets and the Moon from that on the Earth
- Explain that gravitational force causes moons to orbit planets, planets to orbit the Sun, artificial satellites to orbit the Earth, and comets to orbit the Sun
- Describe the differences in the orbits of comets, moons and planets
- Use the relationship between orbital speed, orbital radius and time period: orbital speed = 2 x pi x orbital radius / time period
Mind map
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Flashcards
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Motion In The Universe. 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.
- Which of the following correctly describes the structure of the universe? A) Stars contain galaxies which contain solar systems B) The universe contains galaxies which contain solar systems C) Solar systems contain galaxies which contain stars D) Galaxies contain universes which contain stars Answer: B
- What happens to the orbital speed of a planet as its distance from the Sun increases? A) It increases B) It stays the same C) It decreases D) It doubles Answer: C
- Which type of orbit do comets follow around the Sun? A) Circular B) Slightly elliptical C) Highly elliptical D) Parabolic Answer: C
- The gravitational field strength on the Moon is about 1.6 N/kg. What is the weight of a 50 kg object on the Moon? A) 50 N B) 80 N C) 500 N D) 31.25 N Answer: B
- What provides the centripetal force that keeps a planet in orbit around the Sun? A) The planet's own rotation B) Friction with space dust C) Gravitational attraction between the planet and the Sun D) Magnetic force from the Sun Answer: C
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Recommended Books
Further learning from open sources
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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
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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
Published by other organisations under open licences, credited as they ask. Links open their websites.
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