Orbital motion of artificial satellites: relationship between radius and speed
Lesson details
Learning outcome
I can describe changes to a satellite’s speed and velocity and explain what happens to its orbital radius if its speed changes.
Key learning points
- Artificial satellites orbit Earth because of the gravitational attraction between them.
- The speed of a satellite along its orbit around Earth is constant.
- The velocity of a satellite along its orbit around Earth constantly changes as it changes direction.
- The centripetal force on a satellite makes it accelerate and change direction, but not speed.
- To orbit in a stable orbit, the orbital radius of a satellite must change if its speed changes.
Keywords
Satellite - an object which orbits a planet; satellites can be natural (moons) or artificial
Polar orbit - an orbit in which the satellite passes over the poles of a planet
Geostationary orbit - an orbit in which the satellite is stationary in the sky as it orbits in the same time as the planet, directly above its equator
Orbital path - the path a satellite takes around the planet it orbits
Orbital radius - the radius of an orbit, measured from the centre of a planet
Common misconception
Motion is always in the direction of the force acting on an object.
Provide pupils with opportunity to experience a radial force changing the direction of a small object in order to make it move in a circular path.
Teacher tip
Demonstrate (with care) the effect of a radial force by releasing a string that is forcing a small object to move in a circular path. The object will continue to move in a straight line in the direction it was travelling when the force is removed.
Equipment
Thin plastic tubes (e.g. shells of ballpoint pens), rubber bung, strong thread, masses and mass holder.
Content guidance
Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.What happens when the Earth orbits the Sun?
Q2.Which of the following objects orbit Earth?
Q3.Which of the following objects orbit only the Sun?
Q4.Starting with the planet with the fewest moons, sort the following planets into increasing order of number of moons.
Q5.How many artificial satellites orbit Earth?
Q6.Starting with the planet that takes the shortest amount of time, sort the following planets into increasing order of how long they take to orbit the Sun.
Assessment exit quiz
6 Questions
Q1.Titan is a large moon of Saturn. Which of the following statements most accurately describes Titan?
Q2.Which of the following types of satellites are often found in low Earth orbits?
Q3.Why are communication satellites usually placed in a circular orbit of 35 785 km above the Equator?
Q4.What force acts on a satellite in geostationary orbit?
Q5.Starting with the satellite that has the fastest orbit, sort the following satellites of Earth into increasing order of how long they take to orbit Earth.
Q6.A satellite in low Earth orbit has an orbital radius of 8000 km and is travelling at a speed of 25 000 km/h. How many times does it orbit Earth in 24 hours?
To help you plan your 11 physics lesson on: Orbital motion of artificial satellites: relationship between radius and speed, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 11 physics lesson on: Orbital motion of artificial satellites: relationship between radius and speed, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 physics lessons from the Gravity in space unit, dive into the full secondary physics curriculum, or learn more about lesson planning.