Read and make notes on the following
The Earth orbits the Sun in a circular orbit. Actually, it is a slightly squashed circle which is called an elliptical orbit.
The force of gravity between the Earth and the Sun holds the Earth in its orbit.
The moon is a natural satellite.
Once again the force of gravity holds the moon in its orbit around the Earth.
Artificial satellites are man-made. Geostationary satellites orbit once every 24 hours.
This website allows you to track satellites in real-time including the space station – https://www.n2yo.com/ also
ISS High Definition Live Streaming Video of the Earth (HDEV)
When objects orbit an object there is a change in velocity.
Velocity is speed with a direction and since the direction is changing there is a change in velocity.
The direction is continuously changing which means that the velocity is constantly changing also.
The speed does not change as it is scalar and does not depend on direction.
If the speed of the satellite changes then the radius of the orbit must also change. This is because at a higher speed, the satellite needs a greater force of gravity to prevent it flying off into space.
By moving closer to the Earth, the gravitational force is greater and the satellite remains in a stable orbit.
This is also true for planets and moons.
GCSE Exam Revision Specification Focus Questions and Answers 