Satellites and moons
3 marks · NormalA comet has an orbit that is much more elongated (stretched out) than the nearly circular orbit of a planet around the Sun.
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A comet moves at changing speeds—very fast close to the Sun, much slower far away—because the gravitational force is stronger when closer to the Sun. Its orbit is elongated and not circular, unlike the planet’s orbit, due to its different speed and position.
Must show: variation in speed, reason for change (gravity stronger when closer), elongated orbit shapes
Common mistakes: Saying a comet’s speed never changes; Not referencing force or distance
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Marking points
B1 · 1 mark · States speed is not constant; comet moves faster close to the Sun.
B2 · 1 mark · Explains that gravitational force is stronger when comet is closer to Sun, causing more rapid motion.
B3 · 1 mark · Correctly describes the shape of comet’s orbit as elongated, not circular.
Worked solution
A comet moves at different speeds through its orbit. It moves much faster when close to the Sun (where gravity is stronger), and much more slowly when farther away. Its orbit is elongated, not circular, because its distance from the Sun changes a lot.