AQA GCSE Physics (8463), Higher tier · Space physics › Solar system, orbits and satellites
Practise Orbital motion and satellites. 15 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Planets, moons and artificial satellites all move in orbits.
(a) Give one similarity between the Moon and an artificial satellite that orbits the Earth.[1]
(b) Give one difference between a planet and a moon.[1]
(c) Give one difference between a moon and an artificial satellite.[1]
(d) Explain why the Earth moves in a circular orbit around the Sun instead of travelling in a straight line through space.[2]
Show the answer and mark scheme
(a)Answer: Both orbit the Earth, held by its gravity.
both orbit the Earth / both are kept in orbit by the Earth's gravity
(b)Answer: Planets orbit the Sun; moons orbit planets.
a planet orbits the Sun (a star), but a moon orbits a planet
(c)Answer: A moon is natural; an artificial satellite is made by people.
a moon is natural, but an artificial satellite was made and launched by people
(d)Answer: The Sun's gravity continually pulls the Earth towards the centre of its orbit, changing its direction of motion.
the Sun's gravity pulls the Earth towards the Sun (towards the centre of the orbit)
this force continually changes the direction in which the Earth is moving
Question 3Hard7 marks
A satellite moves in a circular orbit of radius 7.0 × 106 m around the centre of the Earth. It takes 97 minutes to complete one orbit. distance travelled in one orbit = 2 × π × radius
(a) Calculate the speed of the satellite in m/s.[3]
(b) A second satellite orbits the Earth at a larger radius. Compare the speed of the second satellite and the time it takes to complete one orbit with those of the first satellite.[2]
(c) Explain why the satellite does not need an engine to keep it moving around its orbit.[2]
Show the answer and mark scheme
(a)Answer: 7600 m/s (7560 m/s) m/s
distance = 2 × π × 7.0 × 106 = 4.4 × 107 (m)
time = 97 × 60 = 5820 (s)
v = 4.4 × 107 ÷ 5820 = 7600 (m/s) (7560)
(b)Answer: Lower speed and a longer time for one orbit.
the second satellite has a lower speed
it takes longer to complete one orbit (it travels further at a lower speed)
(c)Answer: With no air resistance nothing slows it down, and gravity supplies the force that keeps it in a circular path.
there is (almost) no air resistance / friction in space, so no force is needed to keep it moving
gravity provides the force that keeps changing its direction, keeping it in the circular orbit