Motion In The Universe
Overview
The Moon has been falling towards the Earth for four and a half thousand million years and has never arrived. Every planet, every moon, every satellite and every comet is held on its path by the same single force, and that force is gravity.
This lesson sets out the scale of the universe, explains why gravitational field strength is different on every world, and shows how gravity produces the very different orbits followed by planets, moons and comets. Expect calculation questions on weight and orbital speed, and explanation questions on why orbits happen at all.
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, causes the planets to orbit the Sun, causes artificial satellites to orbit the Earth, and causes comets to orbit the Sun
- Describe the differences in the orbits of comets, moons and planets
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 force keeps a planet in orbit around the Sun? A) Magnetic force B) Gravitational force C) Electrostatic force D) Friction Answer: B
- The Milky Way is best described as: A) Our solar system B) A galaxy of billions of stars C) The whole universe D) A large comet Answer: B
- An astronaut of mass 75 kg stands on the Moon, where g is 1.6 N/kg. Her weight is: A) 12 N B) 47 N C) 120 N D) 735 N Answer: C
- Where in its orbit does a comet travel fastest? A) When it is furthest from the Sun B) When it is closest to the Sun C) It travels at a constant speed throughout D) When it crosses the orbit of the Earth Answer: B
- Compared with a planet close to the Sun, a planet far from the Sun has: A) A shorter orbital period and a higher speed B) A longer orbital period and a higher speed C) A longer orbital period and a lower speed D) The same orbital period Answer: C
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Practice Mock Questions
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