1. 1
   A trainee presenter at a planetarium is preparing an introductory talk for school visitors about the scale of the universe, from our own solar system within the Milky Way galaxy up to the collection of billions of galaxies that make up the observable universe.

   (a)

   A trainee planetarium presenter is preparing a talk on the scale of the universe and wants to check the correct order of size. Which of these correctly lists structures from smallest to largest?

   [1 mark]

   • ASolar system, galaxy, universe
   • BGalaxy, solar system, universe
   • CUniverse, galaxy, solar system
   • DSolar system, universe, galaxy

   (b)

   During the talk, the presenter explains that our own solar system lies within a specific galaxy. What is the name of this galaxy?

   [1 mark]

   • AThe Big Bang
   • BAndromeda
   • CThe Local Group
   • DThe Milky Way

   (c)

   Describe what is meant by 'the universe' in terms of the number and scale of galaxies it contains, and briefly explain how a galaxy relates to the stars within it.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A space agency engineer is planning the orbit of a newly launched artificial satellite around the Earth, and must calculate its orbital speed based on the radius of its orbit and how long it takes to complete one full orbit.

   (a)

   A space agency engineer is calculating the orbit of a newly launched artificial satellite around the Earth. What force is responsible for keeping the satellite in orbit around the Earth?

   [1 mark]

   • AMagnetic force
   • BElectrostatic force
   • CGravitational force
   • DFriction force

   (b)

   The engineer compares this artificial satellite's circular orbit with the elliptical orbit of a comet around the Sun. Which statement correctly describes a key difference between the orbits of comets and planets?

   [1 mark]

   • AComets orbit planets, while planets orbit the Sun
   • BComets typically follow highly elongated (elliptical) orbits, while most planets follow nearly circular orbits
   • CComets do not experience any gravitational force, while planets do
   • DComets always orbit at a constant, unchanging speed, exactly like planets

   (c)

   The satellite orbits the Earth in a circular path of radius 7000 km, taking 6000 seconds to complete one full orbit. Calculate the orbital speed of the satellite, giving your answer to an appropriate number of significant figures.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An astronaut training team is preparing a crew for a mission that will involve time spent on the surface of both the Moon and, eventually, Mars, and must brief the astronauts on how gravitational effects will differ between the two locations and Earth.

   (a)

   An astronaut training team is preparing crew members for a future crewed mission to the Moon and eventually to Mars. Explain why the gravitational field strength on the surface of the Moon is different from that on the surface of the Earth, and why the astronauts will need to adapt their movements accordingly.

   [3 marks]

   (b)

   Explain why the gravitational field strength on the surface of Mars is expected to be different again from both the Earth and the Moon, and describe how this would affect the orbital speed of a satellite placed in orbit around Mars compared with an identical satellite orbiting the Earth at the same orbital radius.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A science museum is designing a new interactive exhibit to help visitors understand why moons, planets and artificial satellites all stay in orbit, using the concept of gravitational force acting between orbiting bodies.

   (a)

   A science museum is designing a new exhibit explaining why moons, planets and artificial satellites all remain in orbit rather than flying off into space or falling straight down. Explain, using the concept of gravitational force, why moons orbit planets, planets orbit the Sun, and artificial satellites orbit the Earth, and discuss what would happen to each type of orbiting object if the gravitational force suddenly disappeared.

   [6 marks]

   (b)

   The exhibit also compares the orbits of comets with those of planets and moons. Explain the key differences between the orbits of comets and the orbits of planets and moons, and discuss how a comet's speed and distance from the Sun change as it moves along its highly elongated orbit.

   [6 marks]

   Total for question 4: 12 marks

End of questions