Astrophysics: Units
Overview
Astrophysics deals with distances, speeds, and forces on a scale that can feel overwhelming at first. A star might be millions of light-years away, orbiting bodies travel at kilometres per second, and gravitational fields stretch across entire solar systems. Keeping the units under control is the first step toward tackling any calculation in this section.
This lesson gathers the units the Edexcel specification lists for the Astrophysics section, explains what each one measures, and gives you practice converting and applying them. Several of these units (kg, m, N, s) also appear in earlier sections, so this is a chance to consolidate what you already know while adding the astrophysics-specific quantities.
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)
Mind map
This topic is mapped out so you can see how the ideas connect.
Open the mind map in the app
Flashcards
Quick recall practice on the facts this topic is tested on.
Practise these cards in the app
Lesson Note
Complete Note Available on the Green Bridge App
Get the Green Bridge CBT app on your phone or computer for the complete IGCSE library: past papers, mark schemes, mind maps, flashcards and audio lessons.
Lesson Evaluation
Congratulations on completing the lesson on 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.
- What is the SI unit of gravitational field strength? A) m/s2 B) N/kg C) kg/m3 D) Pa Answer: B
- Which pair of units are dimensionally equivalent? A) N and kg B) N/kg and m/s2 C) m/s and m/s2 D) kg and N/kg Answer: B
- The mass of the Earth is approximately 6.0 x 10^24 kg. What unit is this expressed in? A) Grams B) Tonnes C) Kilograms D) Newtons Answer: C
- What unit is orbital speed measured in? A) m/s2 B) N C) m/s D) kg Answer: C
- A planet has g = 3.7 N/kg. An object of mass 20 kg has a weight of: A) 74 N B) 5.4 kg C) 37 N D) 0.19 N/kg Answer: A
Work through these questions in the app
Work through these questions in the app
Recommended Books
Practice Mock Questions
Want to practice mock questions on Astrophysics: Units? Download the Green Bridge CBT app to access mock questions and full practice assessments for this topic.
Download The App On Google Playstore
Everything you need to excel in your exams
