What happens to the force if the distance doubles?

It becomes one quarter of its original size.

What force keeps planets in orbit around the Sun?

The gravitational force of the Sun.

What keeps the Moon in orbit around the Earth?

The gravitational force of the Earth.

What is an orbital period?

The time taken to complete one orbit.

Which planet has the shortest orbital period?

Mercury, the closest planet to the Sun.

How does orbital speed change with distance from the Sun?

Planets further away move more slowly.

Why does a satellite not fly off in a straight line?

Gravity keeps pulling it towards the Earth, changing its direction.

Motion when gravity is the only force acting on an object.

Why do astronauts on the ISS feel weightless?

They and the station are in free fall together, so no floor pushes back on them.

Is there gravity on the ISS?

Yes, about 90% of the value at the Earth's surface.

Gravity in the solar systemIB MYP Physics: Flashcards

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What two things does gravitational force depend on?

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What two things does gravitational force depend on?: The masses of the objects and the distance between them.
How does gravitational force change as distance increases?: It decreases.
What happens to the force if the distance doubles?: It becomes one quarter of its original size.
What force keeps planets in orbit around the Sun?: The gravitational force of the Sun.
What keeps the Moon in orbit around the Earth?: The gravitational force of the Earth.
What is an orbital period?: The time taken to complete one orbit.
Which planet has the shortest orbital period?: Mercury, the closest planet to the Sun.
How does orbital speed change with distance from the Sun?: Planets further away move more slowly.
Why does a satellite not fly off in a straight line?: Gravity keeps pulling it towards the Earth, changing its direction.
What is free fall?: Motion when gravity is the only force acting on an object.
Why do astronauts on the ISS feel weightless?: They and the station are in free fall together, so no floor pushes back on them.
Is there gravity on the ISS?: Yes, about 90% of the value at the Earth's surface.
How long does the ISS take to orbit the Earth?: About 90 minutes.

Exam questions on Gravity in the solar system

Astronomers in Chile compare the planets orbiting the Sun. Mercury is the closest planet to the Sun and Neptune is the furthest.
Explain why Neptune takes much longer than Mercury to orbit the Sun.2 marks
A communications satellite orbits the Earth in a circular path at a constant height. Its engines are switched off.
Explain why the satellite does not move off in a straight line.2 marks
A student collects data about four planets. Mercury is 58 million km from the Sun and has an orbital period of 88 days. Earth is 150 million km away with a period of 365 days. Mars is 228 million km away with a period of 687 days. Jupiter is 778 million km away with a period of 4333 days.
Describe the trend in the data and calculate how many times longer Jupiter's orbital period is than Earth's.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).