The Universe is a large collection of billions of galaxies. It is also the name given to the entirety of space.

A galaxy is a large collection of billions of stars.

Define planetary system .

A planetary system is a system in which planets and other astronomical objects orbit around a star at the centre.

The Earth is the third of ______ planets in our Solar System.

The Earth is the third of eight planets in our Solar System.

True or False? The Universe is a large collection of billions of stars.

False. The Universe is a large collection of billions of galaxies ; a galaxy is a large collection of billions of stars.

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

How does the gravitational field strength on the surface of the Moon compare to the Earth's, and what effect does this have?

It is less than on Earth, so it would be easier to lift a mass on the surface of the Moon.

How does the gravitational field strength on the surface of a gas giant (e.g. Jupiter) compare to the Earth's, and what effect does this have?

It is more than on Earth, so it would be harder to lift a mass on the gas giant.

The greater the ______ of a planet, the greater its gravitational field strength.

The greater the mass of a planet, the greater its gravitational field strength.

Give three effects of an object's weight.

Weight keeps objects firmly on the ground, causes objects to fall to the ground, and keeps satellites in orbit.

True or False? An object's mass changes depending on which planet it is on, but its weight stays the same.

False. An object's mass stays the same on different planets, but its weight changes because gravitational field strength varies from planet to planet.

What causes the orbital motion of one astronomical body around another?

The gravitational force of attraction between the two bodies. This force always acts towards the centre of the larger body, causing the orbiting body to move in a circular path .

Comets orbit the ______ , while moons orbit ______ .

Comets orbit the Sun , while moons orbit planets .

Define an elliptical orbit .

An elliptical orbit is a stretched circular orbit. Planets follow slightly elliptical orbits with the Sun at one focus.

How does a planet's orbital speed and orbital period relate to its distance from the Sun?

The further a planet is from the Sun, the slower it travels and the longer it takes to complete an orbit.

Give three similarities between the orbits of the planets in the Solar System.

Any three from: their orbits are all slightly elliptical with the Sun at one focus, they all orbit in the same plane , and they all travel in the same direction around the Sun.

How does a comet's orbital speed change as it moves around the Sun?

Its speed increases as it approaches the Sun and decreases as it moves further away.

How does the distance of a moon from its planet affect its orbital period and speed?

The closer the moon is to the planet, the shorter its orbital period and the greater its orbital speed.

True or False? All comets orbit the Sun in the same plane and same direction as the planets.

False. Not all comets orbit in the same plane as the planets, and some comets do not orbit in the same direction.

Define orbital period .

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

The distance travelled by an object in one orbit is equal to the ______ of its circular orbit, 2π r .

The distance travelled by an object in one orbit is equal to the circumference of its circular orbit, 2π r .

From which point is the orbital radius r always measured?

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

What two unit conversions are typically needed before substituting values into the orbital speed equation?

Convert the orbital period into seconds , and convert the orbital radius into metres .

IGCSEPhysicsEdexcelPhysics (Modular)Unit 2Flashcards9. AstrophysicsMotion in the Universe

Motion in the Universe (Edexcel IGCSE Physics (Modular): Unit 2): Flashcards

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FrontObjects in Space
Define Universe.

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Cards in this collection (28)

Define Universe.
The Universe is a large collection of billions of galaxies. It is also the name given to the entirety of space.
Define galaxy.
A galaxy is a large collection of billions of stars.
Define planetary system.
A planetary system is a system in which planets and other astronomical objects orbit around a star at the centre.
Which galaxy is our Solar System part of?
The Milky Way galaxy.
What object lies at the centre of our Solar System?
The Sun, a star.
The Earth is the third of ______ planets in our Solar System.
The Earth is the third of eight planets in our Solar System.
True or False?
The Universe is a large collection of billions of stars.
False.
The Universe is a large collection of billions of galaxies; a galaxy is a large collection of billions of stars.
Define weight.
Weight is the force acting on an object due to gravitational attraction.
What is the approximate gravitational field strength (g) at the Earth's surface?
10 N/kg.
How does the gravitational field strength on the surface of the Moon compare to the Earth's, and what effect does this have?
It is less than on Earth, so it would be easier to lift a mass on the surface of the Moon.
How does the gravitational field strength on the surface of a gas giant (e.g. Jupiter) compare to the Earth's, and what effect does this have?
It is more than on Earth, so it would be harder to lift a mass on the gas giant.
The greater the ______ of a planet, the greater its gravitational field strength.
The greater the mass of a planet, the greater its gravitational field strength.
Give three effects of an object's weight.
Weight keeps objects firmly on the ground, causes objects to fall to the ground, and keeps satellites in orbit.
True or False?
An object's mass changes depending on which planet it is on, but its weight stays the same.
False.
An object's mass stays the same on different planets, but its weight changes because gravitational field strength varies from planet to planet.
What causes the orbital motion of one astronomical body around another?
The gravitational force of attraction between the two bodies. This force always acts towards the centre of the larger body, causing the orbiting body to move in a circular path.
Comets orbit the ______, while moons orbit ______.
Comets orbit the Sun, while moons orbit planets.
Define an elliptical orbit.
An elliptical orbit is a stretched circular orbit. Planets follow slightly elliptical orbits with the Sun at one focus.
How does a planet's orbital speed and orbital period relate to its distance from the Sun?
The further a planet is from the Sun, the slower it travels and the longer it takes to complete an orbit.
Give three similarities between the orbits of the planets in the Solar System.
Any three from: their orbits are all slightly elliptical with the Sun at one focus, they all orbit in the same plane, and they all travel in the same direction around the Sun.
How does a comet's orbital speed change as it moves around the Sun?
Its speed increases as it approaches the Sun and decreases as it moves further away.
How does the distance of a moon from its planet affect its orbital period and speed?
The closer the moon is to the planet, the shorter its orbital period and the greater its orbital speed.
True or False?
All comets orbit the Sun in the same plane and same direction as the planets.
False.
Not all comets orbit in the same plane as the planets, and some comets do not orbit in the same direction.
Define orbital period.
The orbital period is the time taken for an object to complete one orbit.
What is the equation for orbital speed, and what does each symbol represent?
$v = \frac{2 π r}{T}$
Where v = orbital speed (m/s), r = average orbital radius (m), T = orbital period (s).
The distance travelled by an object in one orbit is equal to the ______ of its circular orbit, 2πr.
The distance travelled by an object in one orbit is equal to the circumference of its circular orbit, 2πr.
From which point is the orbital radius r always measured?
From the centre of the object being orbited to the object orbiting it.
What two unit conversions are typically needed before substituting values into the orbital speed equation?
Convert the orbital period into seconds, and convert the orbital radius into metres.
True or False?
Orbital speed can be found using speed = distance ÷ time, where the distance is the circumference of the orbit.
True.
Speed = distance ÷ time, and the distance travelled in one orbit is the circumference of the circular path, 2πr, giving $v = \frac{2 π r}{T}$ .

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