Astronomers observe a planet completing a circular orbit around a distant star. Measurements show that the planet's speed is unchanged.
Which statement is correct?
The planet is not accelerating, because the resultant force on the planet is zero.
The planet is accelerating, because the star's gravity keeps changing the direction of its velocity.
The planet is accelerating, because the star's gravity pushes it forwards along its orbit.
The planet is not accelerating, because the star's gravity acts at right angles to its motion.
84 exam-style questions on AQA GCSE Physics 8.1 Solar system; stability of orbital motions; satellites, covering 8.1.1 Our solar system, 8.1.2 The life cycle of a star, and 8.1.3 Orbital motion, natural and artificial satellites. Each one has a worked solution and a mark scheme showing where the marks go.