Lo and Petrasek each made four 3-pointers for Columbia (13-6, 2-0), which leads the Ivy League comfortably in 3-point makes and attempts. The Lions shot 13 of 24 from beyond the arc, including a 6-for-9 second-half performance.
Cornell (7-9, 0-2) made just five of 26 3-point attempts, with four makes from Matt Morgan, who led the Big Red with 26 points on 9-of-23 shooting.
Columbia led by three at the half but a quick 8-0 run pushed its lead to double digits.
A jumper and two free throws from Morgan closed the gap to seven with 3:53 left, but Petrasek answered with a 3, and the Lions made 6 of 8 free throws down the stretch to close it out.