requires a centripetal force of, mass*velocity 2 /radius = Mer*vt 2 /au = 5.9722E24_kg*(29,785.9_m/s) 2 /149.598E9_m = 3.5418E22_kg*m/s 2 . Force resisted by steel: Ultimate strength is quoted force per unit of cross section area (N/m²). The SI unit of stress is the pascal, where 1_Pa = 1_N/m 2 = 1_kg/(m*s