Physics: Astrophysics: Units
Overview
Astrophysics uses exactly the same units as the rest of mechanics, but stretched to sizes that no laboratory ever meets. The Sun is a hundred and fifty thousand million metres away, a year is thirty million seconds long, and gravitational field strength changes completely depending on which world you happen to be standing on.
This lesson covers the kilogram, metre, second, metre per second, metre per second squared, newton and newton per kilogram as they are used in astronomy. You will practise standard form, convert astronomical times and distances into SI units, and use unit checks to catch the sort of error that a very large number hides well.
Objectives
- Use the following units: kilogram (kg), metre (m), metre/second (m/s), metre/second2 (m/s2), newton (N), second (s), newton/kilogram (N/kg)
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Physics: Astrophysics: Units. 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.
- The SI unit of gravitational field strength is the: A) Newton B) Newton per kilogram C) Kilogram per newton D) Metre per second Answer: B
- The distance 384 000 km written in metres in standard form is: A) 3.84 x 10^5 m B) 3.84 x 10^6 m C) 3.84 x 10^8 m D) 3.84 x 10^11 m Answer: C
- A light-year is a unit of: A) Time B) Distance C) Speed D) Brightness Answer: B
- An astronaut of mass 80 kg stands on a moon where g is 2.0 N/kg. Her weight there is: A) 40 N B) 80 N C) 160 N D) 784 N Answer: C
- Approximately how many seconds are there in one year? A) 3.15 x 10^5 s B) 3.15 x 10^6 s C) 3.15 x 10^7 s D) 3.15 x 10^9 s Answer: C
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