In Larry Niven's science-fiction novel Ringworld, a rigid ring of material rotates about a star. The inhabitants of this ring world live on the starlit inner surface of the ring (where it is always noon). The tangential speed of the ring is 1.25x10^6 m/s, its radius is 1.58x10^11 m, and the star has a mass of 2.2x10^32 kg.
2 answers
v^2/r
v^2/r = ac