Planets, comets and artificial satellites all move in orbits.
Explain how the force of gravity keeps these objects in their orbits.
Your answer should refer to how the speed of an object in a stable orbit is related to the radius of its orbit.
80 exam-style questions on Edexcel GCSE Physics 7.1 The Solar System and gravity, covering 7.1.1 Weight and g on different bodies in space, 7.1.2 The Solar System, 7.1.3 Changing ideas about the Solar System, 7.1.4 Orbits of moons, planets, comets and satellites, and 7.1.5 Gravity and orbital motion. Each one has a worked solution and a mark scheme showing where the marks go.