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Primary General Studies: Earth, Moon and Sun (Paper 4 (error clinic))
Primary General Studies: Earth, Moon and Sun (Paper 4 (error clinic))
This paper repeats the concepts and calculations that go wrong most often, focusing on spin, orbit, synchronous rotation and phases.
Direct answers Check units and rounding before the arithmetic, then check the order of the bodies; if a question fails twice, reread the note.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: Primary General Studies: Earth, Moon and Sun |
| Level | P5 |
02 Questions (10 items)
- FoundationWhat natural change is caused by the spin of Earth?
- FoundationWhat natural change is caused by the orbit of Earth around the Sun?
- FoundationIn astronomy, what is the Moon to Earth?
- IntermediateAn instrument weighs 45 kg on the Moon. About how much would it weigh in Hong Kong, where gravity is six times stronger?
- IntermediateAbout 15 days after new moon, which phase should the Moon be in?
- IntermediateEarth turns 15 degrees each hour. How many degrees does it turn in 8 hours?
- ChallengeSuppose the spin of Earth slowed so that a day lasted 30 hours. How many hours would a week have?
- ChallengeThe Moon orbits every 27.3 days and half a year is about 182.5 days. About how many orbits is that, to one decimal place?
- ChallengeThe Moon is about 384,400 km away and light travels 300,000 km per second. About how many seconds does a signal take to go there and back, to two decimal places?
- Error redoA classmate says the Moon does not spin, which is why the same face always points at Earth. What is correct?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | It causes the alternation of day and night. | One spin takes about 24 hours, so the sunlit side has day while the other side has night. |
| 2 | It causes the change of seasons. | The orbit together with the 23.5 degree tilt changes the angle of sunlight through the year. |
| 3 | It is the natural satellite of Earth. | A natural satellite is a body that formed naturally and orbits a planet, and the Moon is the only one Earth has. |
| 4 | About 270 kg. | 45 times 6 is 270, since the same object weighs more where gravity is stronger. |
| 5 | It should be close to full moon. | The cycle is about 29.5 days, so day 15 sits in the middle and the Moon looks nearly full. |
| 6 | 120 degrees. | 15 times 8 is 120, which is one third of a full turn. |
| 7 | 210 hours. | 30 times 7 is 210, which is 42 hours more than the present 168 hours. |
| 8 | About 6.7 orbits. | 182.5 divided by 27.3 is about 6.7, so half a year holds six or seven full phase cycles. |
| 9 | About 2.56 seconds. | The round trip is 768,800 km, and dividing by 300,000 gives about 2.56 seconds, so there is a clear delay. |
| 10 | The Moon does spin, but its spin period equals its 27.3 day orbit, so the same face always points at us. | If the Moon truly never spun we would see different sides over a month, so synchronous rotation is the right answer. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
A spin of about 24 hours gives day and night while a 365 day orbit with a 23.5 degree tilt gives the seasons, and eclipses happen at new moon or full moon.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.