(a) What is the rotational energy of a planet about its spin axis? The radius of the planet is 6140 km, its mass is 6.55 1024 kg, and it has a rotational period of 24.0 h. Treat the planet as a sphere of moment of inertia 2/5 MR2.
(b) Suppose the rotational kinetic energy of the planet is decreasing steadily because of tidal friction. Calculate the change in one day, given that the rotational period of 24.0 h decreases by about 11 µs each year. (Let 1 yr = 365 d).