1. 1
   A space agency is planning to place a new communications satellite into a stable circular orbit around the Earth, and engineers must calculate the correct speed for the satellite at its chosen orbital altitude.

   (a)

   What force keeps the satellite moving in its circular orbit?

   [1 mark]

   • AGravitational force, acting as the centripetal force
   • BAir resistance, acting as the centripetal force
   • CMagnetic force from the Earth's core
   • DThe satellite's own engine thrust, acting continuously

   (b)

   While the satellite moves in its circular orbit at a constant speed, what effect does the gravitational force have on its motion?

   [1 mark]

   • AIt changes the satellite's speed, but not its direction
   • BIt changes the satellite's direction of motion, but not its speed
   • CIt has no effect on the satellite's motion at all
   • DIt changes both the satellite's speed and its direction continuously

   (c)

   Explain why the satellite is accelerating even though it travels around its orbit at a constant speed.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A school astronomy club is comparing objects found within the Solar System, including planets, moons, asteroids, dwarf planets and comets, and investigating how their orbital speed relates to their distance from the Sun.

   (a)

   A school astronomy club is comparing two small objects that orbit the Sun: a comet and an asteroid. Which statement correctly describes a key difference between them?

   [1 mark]

   • AA comet is a star, while an asteroid is a planet
   • BA comet always orbits a planet, while an asteroid always orbits the Sun directly
   • CA comet is larger than any planet, while an asteroid is smaller than any moon
   • DA comet is composed largely of ice and dust and often follows a highly elongated orbit, while an asteroid is rocky and typically follows a more circular orbit

   (b)

   The club also compares the orbital speeds of objects at different distances from the Sun. As the distance (orbital radius) from the Sun increases, what generally happens to an object's orbital speed?

   [1 mark]

   • AOrbital speed stays exactly the same at all distances from the Sun
   • BOrbital speed increases as orbital radius increases
   • COrbital speed decreases as orbital radius increases
   • DOrbital speed becomes zero once a certain distance is reached

   (c)

   Explain why an object orbiting further from the Sun has a lower orbital speed than one orbiting closer to the Sun.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Satellite engineers are planning to move an orbiting satellite from its current stable circular orbit into a new, higher stable circular orbit, further from the Earth, and must calculate how its speed needs to change.

   (a)

   Satellite engineers need to move an orbiting satellite from its current circular orbit into a new, higher circular orbit further from the Earth. Describe what must happen to the satellite's orbital speed for it to remain in a stable circular orbit at this greater distance.

   [3 marks]

   (b)

   Explain, using the idea of gravity providing the centripetal force, the full relationship between a satellite's orbital radius and its orbital speed, and how this relationship guides where engineers place satellites requiring different orbital speeds.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A public astronomy talk aims to help the audience understand both the range of objects found within our own Solar System and the vast scale of the wider universe beyond it.

   (a)

   A public astronomy talk explains the different types of object found within the Solar System. Describe the main differences between planets, moons, asteroids, dwarf planets and comets, in terms of their relative size and their motion.

   [6 marks]

   (b)

   Explain the scale of the wider universe beyond the Solar System, and describe where the Sun and the Solar System fit within this bigger picture.

   [6 marks]

   Total for question 4: 12 marks

End of questions