Earth and Space | Forces and Motion

A stable orbit for a satellite

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Modelling a stable orbit.

Here you compare the distance the satellite is carried sideways away from the Earth by its own motion and the distance that it falls towards the Earth due to the pull of gravity over the same time interval. You then show how balancing these can give a path that keeps the satellite a constant height above the planet, so in an orbit. The satellite falls away from a straight line.

What to Prepare

  • the modelling program VnR running on a computer connected to a large display.

What Happens During this Activity

Use the modelling tool to give an account of this diagram.

You might build the model shown in clip 1 or a more complex one as shown in clip 2 (see below).

In both cases it is probably best to build the model up with the class, so some practice beforehand will lead to a more relaxed performance.

You can also take some pressure off by having a pupil do the keyboard work, or by preparing a half completed model, perhaps just listing the variables.

You can also, if needed, go so far as accounting for geostationary satellites, by a simple extension to this last model – the radius affects both the orbital speed and the gravitational force. This model shows the two distances that must be in balance.


Download clips for this activity.

exhibits Orbits
subsumes Moon

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