Define axis (of the Earth).

The axis is an imaginary line running through the north and south poles, about which the Earth rotates.

A satellite is a smaller body that orbits a larger body in space. The Moon is a natural satellite of the Earth.

What causes day and night on Earth?

The Earth's rotation on its axis. The half of the Earth's surface facing the Sun experiences day ; the half facing away experiences night .

State the Earth's period of rotation and its period of orbit around the Sun.

The Earth completes one rotation on its axis every 24 hours (1 day), and one orbit of the Sun every 365 days (1 year).

The Earth's axis is tilted at an angle of approximately ______ .

The Earth's axis is tilted at an angle of approximately 23.5° .

What causes the seasons on Earth?

The combination of the Earth's orbit around the Sun and the tilt of its axis.

Why do we always see the same side of the Moon from Earth?

The Moon rotates on its own axis once every month (around 28 days) — the same time it takes to orbit the Earth — so the same hemisphere always faces us.

True or False? The Moon produces its own light.

False. The Moon shines with reflected light from the Sun; it does not produce its own light.

Define orbital period .

The orbital period (time period) is the time taken for an object to complete one orbit.

From where is the orbital radius, r , always measured?

From the centre of the object being orbited to the object that is orbiting it.

In one orbit, a planet travels a distance equal to the ______ of its circular orbit.

In one orbit, a planet travels a distance equal to the circumference of its circular orbit.

True or False? The orbital period must always be converted into seconds before being used in the orbital speed equation.

True. The orbital speed equation gives v in m/s, so T must be in seconds for the units to be consistent.

What two quantities, along with a constant factor, determine an object's average orbital speed in the equation v = 2π r / T ?

Its orbital radius ( r ) and its orbital period ( T ).

An asteroid is a small rocky object that orbits the Sun. Most are found in the asteroid belt , between Mars and Jupiter.

A comet is a body made of dust and ice that orbits the Sun in a different orbit to those of the planets. Its tail forms when the ice melts as it approaches the Sun.

List the components that make up the Solar System.

The Sun , eight planets , natural and artificial satellites , dwarf planets , and asteroids and comets .

How does a planet's gravitational field differ from a dwarf planet's gravitational field, in terms of nearby objects?

A planet's gravitational field is strong enough to have pulled in all nearby objects (except natural satellites). A dwarf planet's gravitational field is not strong enough to have done so.

The eight planets, in order of increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and ______ .

The eight planets, in order of increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune .

Give one example each of a natural satellite and an artificial satellite.

Natural satellite: the Moon (orbits the Earth). Artificial satellite: the International Space Station, ISS (orbits the Earth).

True or False? The speed of light is constant everywhere in the Universe.

True. The speed of light is 3 × 10⁸ m/s and is constant throughout the Universe.

How does a planet's distance from the Sun affect its surface temperature, and why?

The closer a planet is to the Sun, the hotter its surface temperature, because planets nearer the Sun receive a greater proportion of the emitted heat radiation than planets further away.

How does a planet's distance from the Sun affect its orbital period, and why?

The closer a planet is to the Sun, the shorter its orbital period, because the Sun's gravitational field is stronger nearer the Sun, so closer planets move faster and have a shorter distance to travel.

How does a planet's distance from the Sun relate to its density?

The four planets closest to the Sun (Mercury, Venus, Earth, Mars) have the greatest densities (around 4000–5000 kg/m³). The four furthest planets (Jupiter, Saturn, Uranus, Neptune) have the lowest densities (around 1000–2000 kg/m³).

Why do the four planets closest to the Sun have a higher density than the four furthest planets?

The inner planets formed in the hotter inner regions of the early Solar System, where higher-density material (rocks and metals) collected. The outer planets formed in the cooler outer regions , where lower-density material (water and gases) collected.

Venus has a hotter surface temperature than Mercury, even though it is further from the Sun, because its dense atmosphere ______ heat.

Venus has a hotter surface temperature than Mercury, even though it is further from the Sun, because its dense atmosphere traps heat.

True or False? The planet closest to the Sun always has the hottest surface temperature.

False. Mercury is closest to the Sun, but Venus has a hotter surface temperature, due to its dense atmosphere trapping heat.

Name two variables, other than orbital period, whose data can be compared against a planet's distance from the Sun.

Surface temperature and density (surface gravitational field strength is also given in the data).

Weight is the force acting on an object due to gravitational attraction.

How does a planet's gravitational field strength relate to its mass?

The greater the mass of a planet, the greater its gravitational field strength. A higher gravitational field strength produces a larger attractive force towards the planet's centre .

Compare the surface gravitational field strength of the Moon and Jupiter with that of the Earth ( g ≈ 10 N/kg).

The Moon's surface gravitational field strength is less than the Earth's, so it is easier to lift a mass there. Jupiter's is greater than the Earth's, so it is harder to lift a mass there.

What provides the force that keeps a planet in orbit around the Sun, and in what direction does it act?

The gravitational attraction of the Sun, which acts towards the centre of the Sun.

Planets, minor planets and comets travel in ______ orbits, not perfect circles.

Planets, minor planets and comets travel in elliptical orbits, not perfect circles.

How do the strength of the Sun's gravitational field on a planet, and the planet's orbital speed, change as distance from the Sun increases?

Both decrease : the Sun's gravitational field strength on the planet weakens with distance, and the planet's orbital speed also decreases.

True or False? The Sun is at the centre of a planet's elliptical orbit.

False. The Sun is not at the centre of an elliptical orbit — this is only the case for an orbit that is approximately circular .

O LevelPhysicsCambridge (CIE)Flashcards6. Space Physics6.1 Earth & The Solar System

6.1 Earth & The Solar System (Cambridge (CIE) O Level Physics): Flashcards

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FrontThe Earth, Moon & Sun
Define axis (of the Earth).

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Cards in this collection (37)

Define axis (of the Earth).
The axis is an imaginary line running through the north and south poles, about which the Earth rotates.
Define satellite.
A satellite is a smaller body that orbits a larger body in space. The Moon is a natural satellite of the Earth.
What causes day and night on Earth?
The Earth's rotation on its axis. The half of the Earth's surface facing the Sun experiences day; the half facing away experiences night.
State the Earth's period of rotation and its period of orbit around the Sun.
The Earth completes one rotation on its axis every 24 hours (1 day), and one orbit of the Sun every 365 days (1 year).
The Earth's axis is tilted at an angle of approximately ______.
The Earth's axis is tilted at an angle of approximately 23.5°.
What causes the seasons on Earth?
The combination of the Earth's orbit around the Sun and the tilt of its axis.
Why do we always see the same side of the Moon from Earth?
The Moon rotates on its own axis once every month (around 28 days) — the same time it takes to orbit the Earth — so the same hemisphere always faces us.
True or False?
The Moon produces its own light.
False.
The Moon shines with reflected light from the Sun; it does not produce its own light.
Define orbital period.
The orbital period (time period) is the time taken for an object to complete one orbit.
State the equation for orbital speed, defining each symbol.
$v = \frac{2 π r}{T}$
Where:
- v = orbital speed in metres per second (m/s)
- r = average orbital radius in metres (m)
- T = orbital period in seconds (s)
From where is the orbital radius, r, always measured?
From the centre of the object being orbited to the object that is orbiting it.
In one orbit, a planet travels a distance equal to the ______ of its circular orbit.
In one orbit, a planet travels a distance equal to the circumference of its circular orbit.
A satellite orbits at a height h above a planet's surface. How is the orbital radius r found for use in the orbital speed equation?
Add the planet's radius, R, to the height, h:
$r = R + h$
since the orbital radius must be measured to the centre of the planet, not its surface.
True or False?
The orbital period must always be converted into seconds before being used in the orbital speed equation.
True.
The orbital speed equation gives v in m/s, so T must be in seconds for the units to be consistent.
What two quantities, along with a constant factor, determine an object's average orbital speed in the equation v = 2πr/T?
Its orbital radius (r) and its orbital period (T).
Define asteroid.
An asteroid is a small rocky object that orbits the Sun. Most are found in the asteroid belt, between Mars and Jupiter.
Define comet.
A comet is a body made of dust and ice that orbits the Sun in a different orbit to those of the planets. Its tail forms when the ice melts as it approaches the Sun.
List the components that make up the Solar System.
The Sun, eight planets, natural and artificial satellites, dwarf planets, and asteroids and comets.
How does a planet's gravitational field differ from a dwarf planet's gravitational field, in terms of nearby objects?
A planet's gravitational field is strong enough to have pulled in all nearby objects (except natural satellites). A dwarf planet's gravitational field is not strong enough to have done so.
The eight planets, in order of increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and ______.
The eight planets, in order of increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Give one example each of a natural satellite and an artificial satellite.
Natural satellite: the Moon (orbits the Earth).
Artificial satellite: the International Space Station, ISS (orbits the Earth).
How long does light from the Sun take to reach the Earth?
8 minutes.
True or False?
The speed of light is constant everywhere in the Universe.
True.
The speed of light is 3 × 10⁸ m/s and is constant throughout the Universe.
How does a planet's distance from the Sun affect its surface temperature, and why?
The closer a planet is to the Sun, the hotter its surface temperature, because planets nearer the Sun receive a greater proportion of the emitted heat radiation than planets further away.
How does a planet's distance from the Sun affect its orbital period, and why?
The closer a planet is to the Sun, the shorter its orbital period, because the Sun's gravitational field is stronger nearer the Sun, so closer planets move faster and have a shorter distance to travel.
How does a planet's distance from the Sun relate to its density?
The four planets closest to the Sun (Mercury, Venus, Earth, Mars) have the greatest densities (around 4000–5000 kg/m³). The four furthest planets (Jupiter, Saturn, Uranus, Neptune) have the lowest densities (around 1000–2000 kg/m³).
Why do the four planets closest to the Sun have a higher density than the four furthest planets?
The inner planets formed in the hotter inner regions of the early Solar System, where higher-density material (rocks and metals) collected. The outer planets formed in the cooler outer regions, where lower-density material (water and gases) collected.
Venus has a hotter surface temperature than Mercury, even though it is further from the Sun, because its dense atmosphere ______ heat.
Venus has a hotter surface temperature than Mercury, even though it is further from the Sun, because its dense atmosphere traps heat.
True or False?
The planet closest to the Sun always has the hottest surface temperature.
False.
Mercury is closest to the Sun, but Venus has a hotter surface temperature, due to its dense atmosphere trapping heat.
Name two variables, other than orbital period, whose data can be compared against a planet's distance from the Sun.
Surface temperature and density (surface gravitational field strength is also given in the data).
Define weight.
Weight is the force acting on an object due to gravitational attraction.
How does a planet's gravitational field strength relate to its mass?
The greater the mass of a planet, the greater its gravitational field strength. A higher gravitational field strength produces a larger attractive force towards the planet's centre.
Compare the surface gravitational field strength of the Moon and Jupiter with that of the Earth (g ≈ 10 N/kg).
The Moon's surface gravitational field strength is less than the Earth's, so it is easier to lift a mass there. Jupiter's is greater than the Earth's, so it is harder to lift a mass there.
What provides the force that keeps a planet in orbit around the Sun, and in what direction does it act?
The gravitational attraction of the Sun, which acts towards the centre of the Sun.
Planets, minor planets and comets travel in ______ orbits, not perfect circles.
Planets, minor planets and comets travel in elliptical orbits, not perfect circles.
How do the strength of the Sun's gravitational field on a planet, and the planet's orbital speed, change as distance from the Sun increases?
Both decrease: the Sun's gravitational field strength on the planet weakens with distance, and the planet's orbital speed also decreases.
True or False?
The Sun is at the centre of a planet's elliptical orbit.
False.
The Sun is not at the centre of an elliptical orbit — this is only the case for an orbit that is approximately circular.

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