Define Kepler's First Law .

Kepler's First Law states that the orbit of a planet is an ellipse , with the Sun at one of the two foci.

What provides the centripetal force needed for a planet or satellite to stay in a near-circular orbit?

The gravitational force between the orbited body and the orbiting body.

Define geostationary orbit .

An orbit in which a satellite remains above the same point on the Earth's surface at all times, also known as a geosynchronous orbit.

Define Kepler's Second Law .

Kepler's Second Law states that a line segment joining the Sun to a planet sweeps out equal areas in equal time intervals .

A geostationary satellite orbits in the plane of the .......... , directly above it.

A geostationary satellite orbits in the plane of the equator , directly above it.

When the gravitational force is equated to the centripetal force, the mass m of the satellite .......... , meaning all satellites travel at the same speed v in a particular orbit radius r , regardless of their mass.

When the gravitational force is equated to the centripetal force, the mass m of the satellite cancels out , meaning all satellites travel at the same speed v in a particular orbit radius r , regardless of their mass.

In which direction does a geostationary satellite orbit, and why?

West to east — the same direction as the Earth's rotation.

What is the consequence of Kepler's Second Law for a planet's speed during its orbit?

A planet moves faster when nearer the Sun and slower when further away from the Sun.

What is the orbital time period of a geostationary satellite?

24 hours , equal to the Earth's rotational period.

Kepler's First Law states that the orbit of a planet is an .......... , with the Sun at one of the two foci.

Kepler's First Law states that the orbit of a planet is an ellipse , with the Sun at one of the two foci.

Why must the receiver dishes for geostationary satellite signals be pointed towards the same point in the sky?

Because the satellite's orbit is fixed relative to the Earth's surface, so it always appears at the same point in the sky, allowing the receiver dishes to be fixed too.

True or False? Kepler's Third Law only applies to planets orbiting the Sun in our Solar System.

False. Kepler's Third Law applies to any body in orbit about a larger body, such as moons orbiting other planets or exoplanets orbiting foreign stars.

True or False? The gravitational force on an orbiting satellite acts in the same direction as its motion.

False. The gravitational force is centripetal , so it acts perpendicular to the satellite's direction of travel.

Describe the role of a base station and a geostationary satellite in television broadcast.

A base station on Earth sends the TV signal up to the satellite, where it is amplified and broadcast back down to the desired locations on the ground.

Give two examples of orbital systems, other than planets orbiting the Sun, that Kepler's Third Law can be applied to.

The moons orbiting other planets (e.g. the four moons of Jupiter) and exoplanets in orbit about foreign stars.

True or False? A geostationary satellite can orbit above any line of latitude, as long as its orbital period is 24 hours.

False. A geostationary satellite must orbit directly above the equator , in the plane of the equator — a 24-hour period alone is not sufficient.

What useful information can be deduced from measuring the orbital time period and radius of a system using Kepler's Third Law?

The mass of the body being orbited.

Name two uses of geostationary satellites.

Telecommunication transmissions (e.g. radio) and television broadcast .

A LevelPhysicsOCRFlashcards5. Newtonian World & AstrophysicsPlanetary Motion

Planetary Motion (OCR A Level Physics): Flashcards

Exam code: H556

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FrontKepler's Three Laws of Motion
Define Kepler's First Law.

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Cards in this collection (23)

Define Kepler's First Law.
Kepler's First Law states that the orbit of a planet is an ellipse, with the Sun at one of the two foci.
What provides the centripetal force needed for a planet or satellite to stay in a near-circular orbit?
The gravitational force between the orbited body and the orbiting body.
Define geostationary orbit.
An orbit in which a satellite remains above the same point on the Earth's surface at all times, also known as a geosynchronous orbit.
Define Kepler's Second Law.
Kepler's Second Law states that a line segment joining the Sun to a planet sweeps out equal areas in equal time intervals.
State the equation for the orbital speed v of a satellite in terms of G, M and r.
$v = \sqrt{\frac{G M}{r}}$ where M is the mass of the body being orbited and r is the orbital radius.
A geostationary satellite orbits in the plane of the .........., directly above it.
A geostationary satellite orbits in the plane of the equator, directly above it.
Define Kepler's Third Law.
Kepler's Third Law states that the square of the orbital time period T is directly proportional to the cube of the orbital radius r: $T^{2} \propto r^{3}$
When the gravitational force is equated to the centripetal force, the mass m of the satellite .........., meaning all satellites travel at the same speed v in a particular orbit radius r, regardless of their mass.
When the gravitational force is equated to the centripetal force, the mass m of the satellite cancels out, meaning all satellites travel at the same speed v in a particular orbit radius r, regardless of their mass.
In which direction does a geostationary satellite orbit, and why?
West to east — the same direction as the Earth's rotation.
What is the consequence of Kepler's Second Law for a planet's speed during its orbit?
A planet moves faster when nearer the Sun and slower when further away from the Sun.
State the equation for orbital speed v in terms of the orbital radius r and time period T.
$v = \frac{2 π r}{T}$
What is the orbital time period of a geostationary satellite?
24 hours, equal to the Earth's rotational period.
Kepler's First Law states that the orbit of a planet is an .........., with the Sun at one of the two foci.
Kepler's First Law states that the orbit of a planet is an ellipse, with the Sun at one of the two foci.
Derive the equation for Kepler's Third Law, $T^{2} = \frac{4 π^{2} r^{3}}{G M}$ , starting from the two expressions for orbital speed v.
$v^{2} = \frac{G M}{r}$ and $v = \frac{2 π r}{T}$ , so ${(\frac{2 π r}{T})}^{2} = \frac{G M}{r}$ . Expanding and rearranging for T² gives $T^{2} = \frac{4 π^{2} r^{3}}{G M}$ .
Why must the receiver dishes for geostationary satellite signals be pointed towards the same point in the sky?
Because the satellite's orbit is fixed relative to the Earth's surface, so it always appears at the same point in the sky, allowing the receiver dishes to be fixed too.
True or False?
Kepler's Third Law only applies to planets orbiting the Sun in our Solar System.
False.
Kepler's Third Law applies to any body in orbit about a larger body, such as moons orbiting other planets or exoplanets orbiting foreign stars.
True or False?
The gravitational force on an orbiting satellite acts in the same direction as its motion.
False.
The gravitational force is centripetal, so it acts perpendicular to the satellite's direction of travel.
Describe the role of a base station and a geostationary satellite in television broadcast.
A base station on Earth sends the TV signal up to the satellite, where it is amplified and broadcast back down to the desired locations on the ground.
Give two examples of orbital systems, other than planets orbiting the Sun, that Kepler's Third Law can be applied to.
The moons orbiting other planets (e.g. the four moons of Jupiter) and exoplanets in orbit about foreign stars.
In the equation $T^{2} = \frac{4 π^{2} r^{3}}{G M}$ , what does M represent?
The mass of the object being orbited (kg).
True or False?
A geostationary satellite can orbit above any line of latitude, as long as its orbital period is 24 hours.
False.
A geostationary satellite must orbit directly above the equator, in the plane of the equator — a 24-hour period alone is not sufficient.
What useful information can be deduced from measuring the orbital time period and radius of a system using Kepler's Third Law?
The mass of the body being orbited.
Name two uses of geostationary satellites.
Telecommunication transmissions (e.g. radio) and television broadcast.

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