Science lesson plan · 11th grade (Year 12 in England) · 45 minutes
Orbits and orbital speed (v = 2Ï€r / T)
Space
CCSS NGSS.HS-ESS1-4CCSS NGSS.HS-PS2-4England: GCSE Physics: Space physics (orbital motion)
Objective and success criteria
Students will: Orbits and orbital speed (v = 2Ï€r / T).
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Earth's orbit, years and seasons; Scalars and vectors: distance vs displacement, speed vs velocity
Leads to: Newton's law of gravitation and field strength; Circular motion and centripetal force
Materials: Torch and ball for a Sun-Earth-Moon model, Space images, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Earth's orbit, years and seasons; Scalars and vectors: distance vs displacement, speed vs velocity). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- When it is summer in the UK, the Northern Hemisphere is… (not tilted / tilted towards the Sun / furthest from the Sun because of distance / tilted away from the Sun) → tilted towards the SunPrompt: Summer comes with longer days and more direct sunlight.
- Is displacement a scalar or a vector quantity? (scalar (size only) / vector (size and direction)) → vector (size and direction)Prompt: Does it make sense to give it a direction?
- A year is 365 days, plus one extra day every 4 years (a leap year). How many days are there in 4 years in a row? → 1461Prompt: How many leap days are there in 4 years?
Hook · 5 min
- Ask why we see the Moon change shape over a month.
- Share the objective: Orbits and orbital speed (v = 2Ï€r / T). Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: A polar weather satellite orbits at a radius of about 7200 km from Earth's centre, taking 101 minutes per orbit. What is its orbital speed, in km/s? (v = 2πr ÷ T; give 1 decimal place)
- Step 1: T = 101 × 60 = 6060 s
- Step 2: 2π × 7200 = 45239 km
- Step 3: 45239 ÷ 6060 = 7.47
- Step 4: So the answer is: 7.5 km/s
- Answer: 7.5 km/s
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- A geostationary satellite orbits at a radius of about 42160 km from Earth's centre, taking 1436 minutes per orbit. What is its orbital speed, in km/s? (v = 2πr ÷ T; give 1 decimal place) → 3.1 km/sPrompt: Convert the period to seconds.
- A satellite moves at a steady speed in a circular orbit. Why is it accelerating? (Its direction is always changing, so its velocity changes / Its speed increases every orbit / Its engines are always on / It is not accelerating) → Its direction is always changing, so its velocity changesPrompt: Velocity is a vector.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- How does orbital speed change for a smaller (lower) stable orbit? (It must move slower / Speed does not depend on radius / It stops / It must move faster) → It must move fasterPrompt: Gravity is stronger closer to Earth.
- A polar weather satellite orbits at a radius of about 7200 km from Earth's centre, taking 101 minutes per orbit. What is its orbital speed, in km/s? (v = 2πr ÷ T; give 1 decimal place) → 7.5 km/sPrompt: Convert the period to seconds.
Watch out for
- Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
- Remembering facts without the reason: ask "why?" and "what is the evidence?"
Support and stretch
Support
- Review first: Earth's orbit, years and seasons.
- Use concrete materials: torch and ball for a sun-earth-moon model.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Newton's law of gravitation and field strength; Circular motion and centripetal force.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-11.
Free lesson plan from eurekami.com/lesson-plan-builder