| English | Satellite |
|---|---|
| Bahasa Melayu | Satelit |
| 中文 | 卫星 |
Definition
An object that orbits a larger body, such as the Moon around the Earth or a man-made satellite kept in orbit by gravitational force.
In exam terms
A satellite is an object that orbits a larger body, such as the Moon around the Earth, or a man-made satellite kept in orbit by gravitational force. The gravitational pull of the central body provides the centripetal force needed to keep the satellite moving in a circle.
For a stable orbit the gravitational force equals the required centripetal force, which fixes the orbital speed for a given radius. This is written GMm ÷ r² = mv² ÷ r, giving orbital velocity v = √(GM ÷ r), where r is the orbital radius in metres (m).
A satellite closer to Earth must therefore move faster.
Do not confuse it with…
Do not confuse a satellite in general orbit with one in a geostationary orbit. A geostationary satellite has a special orbit above the equator with a period of 24 hours, so it stays above the same point on Earth; most satellites are not geostationary and move relative to the ground.
In Paper 2 you may be asked to explain what keeps a satellite in orbit, or to state that gravitational force provides the centripetal force. Do not say there is an outward force balancing gravity; the net force is the centripetal force acting towards the centre.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)