IGCSE Physics Earth Questions and Worked Solutions (6.1.1) | 0625

By /
IGCSE Physics 0625 · Topic 6.1.1

IGCSE Physics Earth Questions and Worked Solutions

50 topic-wise practice questions on The Earth (Unit 6: Space Physics), written to the Cambridge IGCSE Physics 0625 syllabus for 2026–2028, each with a step-by-step worked solution.

50 questions25 Core15 Extended10 Challenge124 marksTextbook §6.1 · pp. 276–285
Questions tagged Core are for all candidates (Papers 1 & 3). Questions tagged Extended are Supplement content (Papers 2 & 4). Questions 41–50 are harder Challenge questions. Try each question first, then tap Show solution to check your working.

Topic guide: The Earth

The Earth's rotation causes day and night; its orbit and tilted axis cause the seasons; the Moon's orbit causes its phases. (Extended) Orbital speed is calculated from the orbit's radius and period.

Key formulas

v = 2 π r ÷ Taverage orbital speed v (m/s), average orbital radius r (m), period T (s)Extended

Prerequisite knowledge

  • Speed = distance ÷ time (1.2)
  • Circumference of a circle = 2πr
  • Converting days and hours to seconds

Exam tips & common mistakes

  • Convert T to seconds before using v = 2πr/T
  • Seasons are caused by tilt, not distance from the Sun
  • The Moon reflects sunlight; phases depend on how much of the lit half we see

Key facts from the syllabus (6.1.1)

  • The Earth rotates on its tilted axis about once every 24 hours — day and night and the Sun's apparent daily motion (rises east, sets west)
  • The Earth orbits the Sun about once every 365 days — seasons (due to the tilted axis)
  • The Moon orbits the Earth about once a month — cycle of phases
  • Extended average orbital speed v = 2πr/T

Textbook: §6.1 Earth and the Solar System, pp. 276–285

1
Core[1 mark]

State how long the Earth takes to rotate once on its axis.

Show solutionHide solution

Method: ~24 h.

About 24 hours
2
Core[2 marks]

Explain why we have day and night.

Show solutionHide solution

Method: Rotation.

The Earth rotates on its axis, so each place faces towards then away from the Sun
3
Core[2 marks]

Explain why the Sun appears to move across the sky.

Show solutionHide solution

Method: Earth spins.

The Earth rotates from west to east, so the Sun appears to rise in the east and set in the west
4
Core[1 mark]

State how long the Earth takes to orbit the Sun.

Show solutionHide solution

Method: ~365 days.

About 365 days
5
Core[3 marks]

Explain why the Earth has seasons.

Show solutionHide solution

Method: Axis tilt.

The Earth's axis is tilted; as it orbits, each hemisphere is tilted towards the Sun for part of the year (summer: longer days, more direct sunlight) and away for part (winter)
6
Core[2 marks]

Explain why it is summer in the southern hemisphere when it is winter in the northern hemisphere.

Show solutionHide solution

Method: Opposite tilt.

When the north is tilted away from the Sun, the south is tilted towards it
7
Core[1 mark]

State how long the Moon takes to orbit the Earth.

Show solutionHide solution

Method: ~1 month.

About one month
8
Core[3 marks]

Explain why the Moon shows phases.

Show solutionHide solution

Method: Sunlit half seen at different angles.

Half the Moon is always lit by the Sun; as it orbits the Earth we see different amounts of the lit half
9
Core[1 mark]

State the phase of the Moon when it is between the Earth and the Sun.

Show solutionHide solution

Method: New moon.

New moon
10
Core[2 marks]

Explain why days are longer in summer.

Show solutionHide solution

Method: Tilt.

The hemisphere is tilted towards the Sun, so the Sun spends more time above the horizon
11
Core[1 mark]

State the shape of the Sun's path across the sky in the daytime.

Show solutionHide solution

Method: Arc.

An arc from east to west
12
Core[2 marks]

Explain why the Moon always shows the same face to the Earth.

Show solutionHide solution

Method: Rotation = orbit period.

It rotates once on its axis in the same time as it orbits the Earth
13
Core[1 mark]

State the approximate time between two full moons.

Show solutionHide solution

Method: ~1 month.

About one month (29.5 days)
14
Core[2 marks]

State the direction in which the Sun appears to rise and set.

Show solutionHide solution

Method: East to west.

Rises in the east and sets in the west
15
Core[2 marks]

State why the Sun is highest in the sky at midday.

Show solutionHide solution

Method: Earth's rotation.

That place is facing most directly towards the Sun
16
Core[2 marks]

State what causes the change in the length of daylight through the year.

Show solutionHide solution

Method: Tilt and orbit.

The tilt of the Earth's axis as it orbits the Sun
17
Core[2 marks]

State the approximate angle of tilt of the Earth's axis.

Show solutionHide solution

Method: 23.5°.

About 23.5°
18
Core[2 marks]

Explain why sunlight is more intense in summer.

Show solutionHide solution

Method: Higher Sun.

The Sun is higher in the sky, so its light is spread over a smaller area
19
Core[2 marks]

State the phase of the Moon when the Earth is between the Sun and the Moon.

Show solutionHide solution

Method: Full moon.

Full moon
20
Core[2 marks]

State the approximate time between a new moon and a full moon.

Show solutionHide solution

Method: Half month.

About two weeks
21
Core[2 marks]

Explain why the Moon is visible though it produces no light.

Show solutionHide solution

Method: Reflects sunlight.

It reflects light from the Sun
22
Core[2 marks]

Explain why the seasons are not caused by changing distance from the Sun.

Show solutionHide solution

Method: Hemispheres opposite.

The hemispheres have opposite seasons at the same time, which distance cannot explain
23
Core[2 marks]

State how many times the Earth rotates during one orbit of the Sun.

Show solutionHide solution

Method: ~365.

About 365 times
24
Core[2 marks]

State what is meant by one day.

Show solutionHide solution

Method: One rotation.

The time for the Earth to rotate once on its axis (about 24 hours)
25
Core[2 marks]

State what is meant by one year.

Show solutionHide solution

Method: One orbit.

The time for the Earth to orbit the Sun once (about 365 days)
26
Extended[1 mark]

State the equation for average orbital speed.

Show solutionHide solution

Method: v = 2πr/T.

v = 2πr ÷ T
27
Extended[3 marks]

The Earth orbits the Sun at an average radius of 1.5 × 10¹¹ m in 365 days. Calculate its average orbital speed.

Show solutionHide solution

Method: T in seconds.

T = 3.15 × 10⁷ s; v = 2π × 1.5×10¹¹ ÷ T = 2.99 × 10⁴ m/s
28
Extended[3 marks]

The Moon orbits the Earth at radius 3.84 × 10⁸ m in 27.3 days. Calculate its orbital speed.

Show solutionHide solution

Method: T = 27.3 × 86400 s.

v = 1020 m/s
29
Extended[3 marks]

A satellite orbits at radius 7.0 × 10⁶ m with speed 7500 m/s. Calculate its orbital period.

Show solutionHide solution

Method: T = 2πr/v.

T = 2π × 7.0×10⁶ ÷ 7500 = 5860 s
30
Extended[3 marks]

A geostationary satellite has period 24 h and orbital radius 4.2 × 10⁷ m. Calculate its speed.

Show solutionHide solution

Method: T = 86 400 s.

v = 3050 m/s
31
Extended[3 marks]

A planet orbits at 3.0 km/s with period 2.0 × 10⁸ s. Calculate its orbital radius.

Show solutionHide solution

Method: r = vT/2π.

r = 3000 × 2.0×10⁸ ÷ 2π = 9.5 × 10¹⁰ m
32
Extended[2 marks]

State what r and T represent in the orbital speed equation.

Show solutionHide solution

Method: Average radius, period.

r = average radius of the orbit; T = orbital period
33
Extended[3 marks]

Mars orbits the Sun at average radius 2.3 × 10¹¹ m with a period of 687 days. Calculate its orbital speed.

Show solutionHide solution

Method: v = 2πr/T.

v = 24300 m/s
34
Extended[3 marks]

The ISS orbits at radius 6.8 × 10⁶ m with period 92 minutes. Calculate its orbital speed.

Show solutionHide solution

Method: T = 5520 s.

v = 7740 m/s
35
Extended[3 marks]

A moon orbits at 1.5 km/s with radius 4.0 × 10⁸ m. Calculate its period in days.

Show solutionHide solution

Method: T = 2πr/v.

T = 19.4 days
36
Extended[3 marks]

Calculate the distance travelled by the Earth in one orbit (r = 1.5 × 10¹¹ m).

Show solutionHide solution

Method: Circumference.

d = 9.4 × 10¹¹ m
37
Extended[2 marks]

State the effect on orbital speed if orbital radius doubles with the same period.

Show solutionHide solution

Method: v ∝ r.

The speed doubles
38
Extended[3 marks]

A satellite at radius 4.2 × 10⁷ m has speed 3070 m/s. Calculate its period in hours.

Show solutionHide solution

Method: T = 2πr/v.

T = 23.9 h
39
Extended[2 marks]

Explain why a geostationary satellite stays above the same point on Earth.

Show solutionHide solution

Method: Period 24 h.

Its orbital period equals the Earth's rotation period (24 h) and it orbits in the same direction above the equator
40
Extended[3 marks]

Jupiter's moon Io orbits at 4.2 × 10⁸ m with period 1.77 days. Calculate its orbital speed.

Show solutionHide solution

Method: v = 2πr/T.

v = 17300 m/s

Challenge questions

Harder, multi-step questions at the top end of the exam. Attempt these once you are confident with the questions above.

41
ChallengeCore[4 marks]

Explain why the Sun appears to rise in the east and set in the west, and why we have day and night.

Show solutionHide solution

Method: Rotation.

The Earth rotates once in about 24 hours from west to east; places turn towards the Sun (day) and away (night), so the Sun appears to move east to west
42
ChallengeCore[4 marks]

Explain why it is summer in the northern hemisphere in June, including the effect on day length and the Sun's height.

Show solutionHide solution

Method: Tilt.

The northern hemisphere is tilted towards the Sun: the Sun is higher in the sky, sunlight is more concentrated and days are longer
43
ChallengeCore[4 marks]

Explain why the Moon goes through phases over about a month.

Show solutionHide solution

Method: Orbit and sunlit half.

The Moon orbits the Earth in about a month; the half facing the Sun is lit, and we see different fractions of that lit half from new moon to full moon and back
44
ChallengeCore[3 marks]

Explain why the distance between the Earth and the Sun does not cause the seasons.

Show solutionHide solution

Method: Opposite hemispheres.

The Earth is closest to the Sun in January, yet it is winter in the north then; the seasons are caused by the tilt
45
ChallengeExtended[4 marks]

The Moon orbits the Earth at 3.84 × 10⁸ m in 27.3 days. Calculate its orbital speed in m/s and km/h.

Show solutionHide solution

Method: v = 2πr/T.

v = 1020 m/s = 3680 km/h
46
ChallengeExtended[4 marks]

A satellite orbits at radius 7.2 × 10⁶ m with speed 7.4 km/s. Calculate its period in minutes and the number of orbits per day.

Show solutionHide solution

Method: T = 2πr/v.

T = 102 min; orbits per day = 14.1
47
ChallengeExtended[4 marks]

Venus orbits the Sun at 1.08 × 10¹¹ m with period 225 days. Calculate its orbital speed and compare it with the Earth's (about 30 km/s).

Show solutionHide solution

Method: v = 2πr/T.

v = 34900 m/s, faster than the Earth (closer to the Sun)
48
ChallengeExtended[4 marks]

A geostationary satellite has period 24 h and speed 3.07 km/s. Calculate its orbital radius and its height above the Earth's surface (Earth radius 6.4 × 10⁶ m).

Show solutionHide solution

Method: r = vT/2π.

r = 4.2 × 10⁷ m; height = 3.6 × 10⁷ m
49
ChallengeExtended[4 marks]

Jupiter orbits the Sun at 7.8 × 10¹¹ m at 13 km/s. Calculate its orbital period in Earth years (1 year = 3.15 × 10⁷ s).

Show solutionHide solution

Method: T = 2πr/v.

T = 3.8 × 10⁸ s = 12.0 years
50
ChallengeExtended[3 marks]

Explain what r represents in v = 2πr/T for an orbit that is not perfectly circular.

Show solutionHide solution

Method: Average radius.

The average radius of the orbit
All IGCSE Physics topics← 5.2.5 Safety Precautions6.1.2 The Solar System →

Book a free trial class

Tell us a little about your requirement.