If G is the universal gravitational constant and ρ is the uniform density of a spherical planet. Then shortest possible period of rotation around a planet can be
The fastest possible rate of rotation around a planet is that for which the gravitational force on material at the equator just barely provides the centripetal force needed for the rotation.Let M be the mass of the planet R its radius and m the mass of a particle on its surface.Then
MRω2max=GMmR2
or ωmax=√GMR3=√G(43πR3ρ)R3
= 2√πGρ3=2πTmin
∴ Tmin=√3πGρ