3 (a) A moon is in a circular orbit of radius r about a planet. The angular speed of the moon in its orbit is 0. The planet and its moon may be considered to be point masses that are isolated in space. Show that r and a are related by the expression Po 2 = constant. Explain your working. [3] (b) Phobos and Deimos are moons that are in circular orbits about the planet Mars. Data for Phobos and Deimos are shown in Fig. 1.1. moon radius of orbit /m period of rotation about Mars Thours 7.65 Phobos Deimos 9.39 x 106 1.99 * 107​