Solar System & Orbital MotionOxford AQA IGCSE Physics: Flashcards

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How many planets orbit the Sun?

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How many planets orbit the Sun?: Eight.
Name the types of objects (other than planets) found in the Solar System.: Moons, asteroids, dwarf planets and comets.
What galaxy is our Solar System part of?: The Milky Way.
Roughly how many galaxies are there in the universe?: Thousands of millions of galaxies.
Roughly how many stars are in a typical galaxy?: Thousands of millions of stars.
What force provides the centripetal force that keeps planets and satellites in orbit?: Gravity.
In which direction does centripetal force act during orbital motion?: Towards the centre of the orbit.
Does centripetal force change an orbiting object's speed?: No — it changes the direction of motion, not the speed.
What happens to centripetal force due to gravity as separation (distance) increases?: It decreases.
What effect does a weaker centripetal force have on orbital speed?: It results in a lower orbital speed.
What is the relationship between orbital radius and orbital speed?: Each orbital radius has a particular orbital speed needed for a stable orbit; a change in orbital speed causes a change in orbital radius.
Is Earth an example of a natural or artificial satellite of the Sun?: Earth is a planet, not classed as a satellite, but the Moon is a natural satellite of the Earth.