The Earth
Cambridge IGCSE Physics (0625) · Unit 6: Space physics · 8 flashcards
The Earth is topic 6.1.1 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 6 — Space physics , alongside The Solar System, The Sun as a star and Stars. In one line: Average orbital speed is the distance travelled in one orbit divided by the orbital period. V = 2πr/T, where V is average orbital speed, r is the average radius of the orbit, and T is the orbital period.
This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).
The deck below contains 8 flashcards — 1 definition — covering the precise wording mark schemes reward. Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
Average orbital speed, stating the meaning of each symbol in the equation used to calculate it
Average orbital speed is the distance travelled in one orbit divided by the orbital period. V = 2πr/T, where V is average orbital speed, r is the average radius of the orbit, and T is the orbital period.
What the Cambridge 0625 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Know Know that the Earth is a planet that rotates on its axis, which is tilted, once in approximately 24 hours, and use this to explain observations of the apparent daily motion of the Sun and the periodic cycle of day and night
- Know Know that the Earth orbits the Sun once in approximately 365 days and use this to explain the periodic nature of the seasons
- Know Know that it takes approximately one month for the Moon to orbit the Earth and use this to explain the periodic nature of the Moon's cycle of phases
- Define Define average orbital speed from the equation V = 2πr/T where r is the average radius of the orbit and T is the orbital period; recall and use this equation Supplement
Explain why we experience day and night on Earth, linking your explanation to the Earth's rotation. (1)
The Earth rotates on its axis. As a location rotates into sunlight, it experiences day. As it rotates away from sunlight, it experiences night.
Suggest why the apparent daily movement of the Sun across the sky is different in the Northern and Southern Hemispheres. (1)
The Earth's axis is tilted relative to its orbit around the Sun. This tilt causes different hemispheres to be exposed to different amounts of direct sunlight throughout the year, altering the apparent path of the Sun.
Explain why the Earth experiencing 365 days in its orbit around the Sun results in the cyclical changes we observe as seasons. (1 mark)
The Earth's axial tilt, coupled with its 365-day orbit, causes different hemispheres to be closer to the Sun at different times, leading to seasonal changes (1 mark).
Suggest how a planet's orbital period around its star impacts the duration and frequency of its seasons, given the Earth's orbital period is 365 days. (1 mark)
A shorter orbital period would lead to more frequent and potentially shorter seasons. A longer period would mean fewer, but potentially longer seasons (1 mark).
Explain why the Moon's phases, such as full moon or new moon, occur approximately once a month (every 29.5 days). (1)
The Moon orbits the Earth approximately once a month. Different amounts of the moon are illuminated by the sun in this periodic orbit. (1)
Suggest why calendars are often based on cycles of roughly 30 days. (1)
The Moon orbits the Earth in approximately one month (29.5 days), giving a natural cycle for tracking time. (1)
Define average orbital speed, stating the meaning of each symbol in the equation used to calculate it.
Average orbital speed is the distance travelled in one orbit divided by the orbital period. V = 2πr/T, where V is average orbital speed, r is the average radius of the orbit, and T is the orbital period.
The Earth orbits the Sun with an average radius of 1.5 x 10¹¹ m and a period of 3.16 x 10⁷ s. Calculate the Earth's average orbital speed.
V = 2πr/T
V = 2π(1.5 x 10¹¹ m) / (3.16 x 10⁷ s)
V = 2.98 x 10⁴ m/s
The average orbital speed is calculated using the formula, substituting given values and solving.
Key Questions: The Earth
Define average orbital speed, stating the meaning of each symbol in the equation used to calculate it.
Average orbital speed is the distance travelled in one orbit divided by the orbital period. V = 2πr/T, where V is average orbital speed, r is the average radius of the orbit, and T is the orbital period.
More topics in Unit 6 — Space physics
The Earth sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this The Earth deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
Related Physics guides
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