I was going through the concepts of Coriolis force but got stuck at the point that the Coriolis force is zero at the equator. Consider a person moving along the equator with a velocity v. Mathematically, Coriolis force= -2m(w x v) In this case though the latitude is zero, the angular velocity vector and the tangential velocity vector are perpendicular. This gives a non zero Coriolis force! I know something is wrong with my reasoning but can't figure it out. The only way out seems that that the 2 vectors are not perpendicular. Something to do with angle between 2 lines in 3-D space? Thanx in advance.